Error during SCIM operation: System.InvalidOperationException: Sequence contains more than one element

I am seeing the above error *sometimes* when attempting to update a user via SCIM.

In every case of the error that I've seen SCIM has been trying to update a single field (Role) which is mapped from Azure's large "appRoleAssignments" XML field value, but I don't actually know if that's relevant or coincidental.

The full stack trace is:

20220428,11:53:00,UNIFYBroker,Logging,Information,Healthcheck,Normal
20220428,11:54:00,UNIFYBroker,Logging,Information,Healthcheck,Normal
20220428,11:54:05,UNIFYBroker,SCIMGateway,Error,"Error during SCIM operation: System.InvalidOperationException: Sequence contains more than one element
at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source)
at Unify.Product.IdentityBroker.SCIMProvider.Patch(IAdapterEntity adapterEntity, PatchRequest2 patch, ISCIMGatewayMapping mappings, IValueAdapter`2 valueAdapter, IEntitySchema schema)
at Unify.Product.IdentityBroker.SCIMProvider.d__20.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.SystemForCrossDomainIdentityManagement.ProviderBase.d__45.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.SystemForCrossDomainIdentityManagement.ProviderAdapterTemplate`1.d__15.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.SystemForCrossDomainIdentityManagement.ControllerTemplate`1.d__5.MoveNext()",Normal
20220428,11:55:00,UNIFYBroker,Logging,Information,Healthcheck,Normal

Here's the Azure provision on demand output that corresponds to the error:

I can't work out why this happens for some user updates, but others go through just fine.  Since I can't packet trace the SCIM protocol in UNIFYConnect environment my ability to debug this is limited, and unfortunately right now I don't really have time to set up a non-UNIFYConnect test environment to debug what's going on.

The backing connector for the SCIM gateway is a PowerShell one, but the error appears to be occurring before it's even called.

I saw https://voice.unifysolutions.net/en/communities/6/topics/3913-sequence-contains-more-than-one-element for the same error, but I am running the latest of everything so the advice on that ticket (upgrade) didn't help.

Do you have any hints what might be going on to result in that error message?