All Clients Showing with Question Mark in MECM Console - ResourceID Issue

All of a sudden (2 weeks ago) all my MECM Clients (~ 4000) in MECM 2409 are showing with a question mark (?) in the console and no values in Last Online Time, Last Activity or HeartBeatDDR. Upon investigation in the statesy.log file on our single site server we see the following message for all clients:

SQL MESSAGE: dbo.spProcessStateReport - The record for machine MYCLIENT (GUID:CF5413C8-1DA7-450D-9243-33DB539DE8FF) was not found in the database. SMS_STATE_SYSTEM 24/09/2025 10:36:45 15356 (0x3BFC)

We then ran MS SQL profiler and see that this external CLR stored proceedure checks for the existince of the client in the SQL view vLocalSystemIDXRef. This view is defined as follows:

create view [dbo].[vLocalSystemIDXRef] as 
select MachineID, GUID from MachineIdGroupXRef 
where ArchitectureKey=5 and 
MachineID between dbo.fnGetSiteRangeStart() and dbo.fnGetSiteRangeEnd() 

The issue is that all clients are actually in the underlying table MachineIdGroupXRef  but due to the filter dbo.fnGetSiteRangeStart() and dbo.fnGetSiteRangeEnd()  they are not part of the view. The reason is their ResourceID is only 4 digits and the value returend from fnGetSiteRangeStart is 16777216.

Q: How could the clients be getting this 4-digit resourceID all of a sudden? We have made no chnagesto MECM (no upgrades, DB restores etc. ).