BackgroundMethodServer reports "ClassCastException: wt.fc.ObjectReference cannot be cast to WfProcessTemplateMasterReference" in Windchill PDMLink

java.lang.ClassCastException: class wt.fc.ObjectReference cannot be cast to class wt.workflow.definer.WfProcessTemplateMasterReference (wt.fc.ObjectReference and wt.workflow.definer.WfProcessTemplateMasterReference are in unnamed module of loader 'app')

wt.util.WTRuntimeException: A persistence error occurred. Nested exception is:
(wt.pom.pomResource/0) wt.pom.PersistenceException: A persistence error occurred. System message follows:
Nested exception is: wt.pom.DatastoreException: A SQL error has occurred. Database system message follows:
Nested exception is: java.lang.ClassCastException: wt.fc.ObjectReference cannot be cast to wt.workflow.definer.WfProcessTemplateMasterReference
at wt.workflow.definer._WfProcessTemplate.readExternal(_WfProcessTemplate.java:718)
at wt.pds.WTResultSet.readObject(WTResultSet.java:679)
at wt.pds.PersistableItemBuilder.build(PersistableItemBuilder.java:559)
at wt.pds.SQLDatabasePds.refresh(SQLDatabasePds.java:2454)
at wt.pds.SQLDatabasePds.refresh(SQLDatabasePds.java:2258)
at wt.pom.PersistentObjectManager.refresh(PersistentObjectManager.java:1477)
at wt.pom.PersistentObjectManager.query(PersistentObjectManager.java:1261)
at wt.fc.StandardPersistenceManager.restore(StandardPersistenceManager.java:1911)
at wt.fc.StandardPersistenceManager.restore(StandardPersistenceManager.java:1161)
at wt.fc.StandardPersistenceManager.restore(StandardPersistenceManager.java:1155)
at wt.fc.cache.ReferenceCache.restore(ReferenceCache.java:312)
at wt.fc.cache.ReferenceCache.get(ReferenceCache.java:303)
at wt.fc.cache.StandardObjReferenceCacheService.getObject(StandardObjReferenceCacheService.java:149)
at sun.reflect.GeneratedMethodAccessor58.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at wt.services.ServiceFactory$ServerInvocationHandler.invoke(ServiceFactory.java:399)