Unable to register new RDS Host via Powershell

I'm having trouble adding a custom Azure Image to an existing WVD Pool. I'm deploying the agents to a new RDS host via the following PowerShell commands (part of a larger script that builds the pool from scratch and adds the hosts):

Invoke-Command -Session $hostSessions -ScriptBlock {Start-Process -FilePath "msiexec.exe" -ArgumentList "/i C:\Support\RDInfraAgentInstall\RDAgent.msi", "/quiet", "/qn", "/norestart", "/passive", "REGISTRATIONTOKEN=$token", "/l* C:\Support\RDAgentInstall.txt" -Wait -Passthru}

Invoke-Command -Session $hostSessions -ScriptBlock {Start-Process -FilePath "msiexec.exe" -ArgumentList "/i C:\Support\RDAgentBootLoaderInstall\RDBootLoader.msi", "/quiet", "/qn", "/norestart", "/passive", "/l* C:\Support\RDBootLoaderInstall.txt" -Wait -Passthru}

Invoke-Command -Session $hostSessions -ScriptBlock {Start-Service RDAgentBootLoader}

Checking the install logs shows that both agents install fine. I can see all variables are correctly populated (including the registration token). However if I look at the WVD pool in the management console no RDS hosts are displayed. Rebooting the hosts doesn't help either. I can see a couple reoccurring errors in the event viewer but nothing particularly helpful:

BootLoader exception:System.AggregateException: One or more errors occurred. ---> System.Exception: Could not resolve a service of type 'Microsoft.RDInfra.ScheduledTasks.HostedServiceExecutor' for the parameter 'hostedServiceExecutor' of method 'Configure' on type 'Microsoft.RDInfra.RDAgent.Service.Startup'. ---> System.ArgumentException: IDX12741: JWT: '[PII is hidden]' must have three segments (JWS) or five segments (JWE).
   at System.IdentityModel.Tokens.Jwt.JwtSecurityToken..ctor(String jwtEncodedString)
   at Microsoft.RDInfra.RDAgent.Service.RDAgentBrokerConfiguration.GetDiagnosticsURI() in C:\agent\_work\14\s\src\RDAgent\src\Service\AgentSettings.cs:line 875
   at Microsoft.RDInfra.Diagnostics.Agent.AgentRestPipelineSinkOptions.Configure(RestPipelineSinkOptions options) in C:\agent\_work\14\s\src\Shared\Diagnostics\src\Microsoft.RDInfra.Diagnostics.Agent\AgentRestPipelineSinkOptions.cs:line 32
   at Microsoft.Extensions.Options.OptionsFactory`1.Create(String name)
   at System.Lazy`1.CreateValue()
   at System.Lazy`1.LazyInitValue()
   at Microsoft.RDInfra.Diagnostics.DataSink.RestPipelineSink..ctor(HttpClient httpClient, ILoggerFactory loggerFactory, IOptions`1 restPipelineSinkOptions, ITokenRetriever tokenRetriever, IMonitoringService monitoringService) in C:\agent\_work\14\s\src\Shared\Diagnostics\src\Microsoft.RDInfra.Diagnostics\DataSink\RestPipelineSink.cs:line 60
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitIEnumerable(IEnumerableCallSite enumerableCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine.<>c__DisplayClass1_0.b__0(ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
   at Microsoft.AspNetCore.Hosting.Internal.ConfigureBuilder.Invoke(Object instance, IApplicationBuilder builder)
   --- End of inner exception stack trace ---
   at Microsoft.AspNetCore.Hosting.Internal.ConfigureBuilder.Invoke(Object instance, IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.ConventionBasedStartup.Configure(IApplicationBuilder app)
   at Microsoft.AspNetCore.Hosting.Internal.WebHost.BuildApplication()
   at Microsoft.AspNetCore.Hosting.Internal.WebHost.d__26.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Hosting.WebHostExtensions.d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Hosting.WebHostExtensions.d__4.MoveNext()
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
   at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
   at Microsoft.RDInfra.RDAgent.Service.RDAgentMain.CreateRDAgentWebHost(String workingDirectory) in C:\agent\_work\14\s\src\RDAgent\src\Service\RDAgentMain.cs:line 69
   at System.Dynamic.UpdateDelegates.UpdateAndExecuteVoid2[T0,T1](CallSite site, T0 arg0, T1 arg1)
   at RDAgentBootLoader.RDAgentBootLoader.d__9.MoveNext() in C:\agent\_work\12\s\src\RDAgent\src\RDAgentBootLoader\RDAgentBootLoader.cs:line 61
---> (Inner Exception #0) System.Exception: Could not resolve a service of type 'Microsoft.RDInfra.ScheduledTasks.HostedServiceExecutor' for the parameter 'hostedServiceExecutor' of method 'Configure' on type 'Microsoft.RDInfra.RDAgent.Service.Startup'. ---> System.ArgumentException: IDX12741: JWT: '[PII is hidden]' must have three segments (JWS) or five segments (JWE).
   at System.IdentityModel.Tokens.Jwt.JwtSecurityToken..ctor(String jwtEncodedString)
   at Microsoft.RDInfra.RDAgent.Service.RDAgentBrokerConfiguration.GetDiagnosticsURI() in C:\agent\_work\14\s\src\RDAgent\src\Service\AgentSettings.cs:line 875
   at Microsoft.RDInfra.Diagnostics.Agent.AgentRestPipelineSinkOptions.Configure(RestPipelineSinkOptions options) in C:\agent\_work\14\s\src\Shared\Diagnostics\src\Microsoft.RDInfra.Diagnostics.Agent\AgentRestPipelineSinkOptions.cs:line 32
   at Microsoft.Extensions.Options.OptionsFactory`1.Create(String name)
   at System.Lazy`1.CreateValue()
   at System.Lazy`1.LazyInitValue()
   at Microsoft.RDInfra.Diagnostics.DataSink.RestPipelineSink..ctor(HttpClient httpClient, ILoggerFactory loggerFactory, IOptions`1 restPipelineSinkOptions, ITokenRetriever tokenRetriever, IMonitoringService monitoringService) in C:\agent\_work\14\s\src\Shared\Diagnostics\src\Microsoft.RDInfra.Diagnostics\DataSink\RestPipelineSink.cs:line 60
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitIEnumerable(IEnumerableCallSite enumerableCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine.<>c__DisplayClass1_0.b__0(ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
   at Microsoft.AspNetCore.Hosting.Internal.ConfigureBuilder.Invoke(Object instance, IApplicationBuilder builder)
   --- End of inner exception stack trace ---
   at Microsoft.AspNetCore.Hosting.Internal.ConfigureBuilder.Invoke(Object instance, IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.ConventionBasedStartup.Configure(IApplicationBuilder app)
   at Microsoft.AspNetCore.Hosting.Internal.WebHost.BuildApplication()
   at Microsoft.AspNetCore.Hosting.Internal.WebHost.d__26.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Hosting.WebHostExtensions.d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Hosting.WebHostExtensions.d__4.MoveNext()<---

No rollback agent provided!

Resetting Agent to RDAgent_1.0.833.5

Even if I manually install the agents afterwards in an RDS host and reboot it still doesn't appear. However if I use Azure Portal to build the pool (with the same custom image) it works fine and builds a new pool with the hosts correctly added.

I can't see why installing the agents via Powershell is failing for my custom image. Anyone else come across this?