List Item Transformers broken in 9.3.0.1 when using SPO Migration Pipeline?

I have a simple listitem transformer that seemed to work fine in 9.2 and now appears to be broken in 9.3.0.1. The transformer skips listitems when they have a certain property. In the transformation step - as a test, i filter by id:

if($dataobject.id -eq 21) {

    $dataobject = $null

}

When using the SPO Azure migration pipeline - this always fails in 9.3.0.1. In fact, it fails to migrate any items in this batch. The error it gives is:

SPO Migration Fatal Error:
Event = JobFatalError
JobId = {JobGuid}
Time = 06/24/2021 09:31:39.194
TotalRetryCount = 0
MigrationType = None
MigrationDirection = Import
ErrorCode = -2146231999
ErrorType = System.Xml.Schema.XmlSchemaValidationException
Message = The element 'Versions' in namespace 'urn:deployment-manifest-schema' has incomplete content. List of possible elements expected: 'File' in namespace 'urn:deployment-manifest-schema'. CallStack -- at System.Xml.Schema.XmlSchemaValidator.SendValidationEvent(ValidationEventHandler eventHandler, Object sender, XmlSchemaValidationException e, XmlSeverityType severity)
at System.Xml.Schema.XmlSchemaValidator.InternalValidateEndElement(XmlSchemaInfo schemaInfo, Object typedValue)
at System.Xml.XsdValidatingReader.ProcessEndElementEvent()
at System.Xml.XsdValidatingReader.ProcessElementEvent()
at System.Xml.XsdValidatingReader.Read()
at Microsoft.SharePoint.Deployment.XmlFormatter.ParseObject(Type objectType, Boolean isChildObject)
at Microsoft.SharePoint.Deployment.XmlFormatter.DeserializeObject(Type objectType, Boolean isChildObject, DeploymentObject envelope)
at Microsoft.SharePoint.Deployment.XmlFormatter.Deserialize(Stream serializationStream)
at Microsoft.SharePoint.Deployment.ObjectSerializer.Deserialize(Stream serializationStream)
at Microsoft.SharePoint.Deployment.SPImport.DeserializeObjects()
at Microsoft.SharePoint.Deployment.SPImport.Run()
CorrelationId = 92f8d49f-c07b-c000-30ac-540a52e3d9d3

SPO Migration End:
Event = JobEnd
JobId = {JobGuid}
Time = 06/24/2021 09:31:39.211
FilesCreated = 0
BytesProcessed = 0
ObjectsProcessed = 2
TotalExpectedSPObjects = 8
TotalErrors = 1
TotalWarnings = 0
TotalRetryCount = 0
MigrationType = None
MigrationDirection = Import
CreatedOrUpdatedFileStatsBySize = {}
ObjectsStatsByType = {"SPUser":{"Count":2,"TotalTime":229,"AccumulatedVersions":0,"ObjectsWithVersions":0},"SPFolder":{"Count":1,"TotalTime":90,"AccumulatedVersions":0,"ObjectsWithVersions":0},"SPDocumentLibrary":{"Count":1,"TotalTime":76,"AccumulatedVersions":0,"ObjectsWithVersions":0}}
CorrelationId = 92f8d49f-c07b-c000-30ac-540a52e3d9d3

Disabling the azure migration piepeline and re-executing the same copy - the migration works and correctly skips the item with the matching id. In my case, it means I cannot use this transformer anymore because not migrating via the azure pipeline is a no-go. Does anyone have a workaround?

Fyi - if you want to reproduce this, you should be able to use either this example or this one: How to flatten a list/library (262524) (quest.com)