I've seen this in two scenarios:
- the newly created object is passed as a parameter to a flow / java action that is executed in it’s own transaction and committed there, but in that case the object doesn’t exist yet in this transaction, throwing this error.
- more likely: the object was deleted by an action earlier in the flow. Look for example for a deleted associated object that also deletes your object through delete behavior (a red or blue association in your domain model).