Seemingly people have an issue with Nvidia GPUs. Me too :(
When ran on the host with Nvidia GTX 980 (latest drivers, 430.39), Sandbox in 18362.86 fails with a 0x80070002 ("file not found") in the error dialog, although in the event log it manifests very differently:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="Microsoft-Windows-Hyper-V-Compute" Guid="{17103e3f-3c6e-4677-bb17-3b267eb5be57}" />
<Keywords>0x4000000000000000</Keywords>
<TimeCreated SystemTime="2019-05-07T02:51:39.479941600Z" />
<EventRecordID>235</EventRecordID>
<Execution ProcessID="5484" ThreadID="16348" />
<Channel>Microsoft-Windows-Hyper-V-Compute-Operational</Channel>
<Computer>Nickel.at.all</Computer>
<Security UserID="S-1-5-18" />
</System>
<UserData>
<VmlEventLog xmlns="http://www.microsoft.com/Windows/Virtualization/Events">
<SystemId>ce0ec531-de7f-4d8a-b92d-b41962529752</SystemId>
<Result>0x80070057</Result>
<Parameter0>{"ResourcePath":"VirtualMachine/ComputeTopology/Gpu","RequestType":"Update","Settings":{"AssignmentMode":"Mirror"}}</Parameter0>
</VmlEventLog>
</UserData>
</Event>
Note different error code. This is only error in the event log, all other records corresponding to same session are successful, with 0x00000000.
Also, when ran inside a Hyper-V VM on the same PC (and same OS build), it runs just fine. No error, no nothing.