Actual behavior: mutable entities are cached and returned to client as is. It introduces subtle bug in querying - queries are executed against original state of entity, but returns only ids, that then is pulled from db, using cache. So if mutated entity may still be returned in query that is matched by it original state, or vice versa, mutated entity may not be returned in query that is matched by it mutated state.

Add cloning of cached entities, before return it to client