Some more poking suggests that rev 14634 broke this.
The code checks update events need to be fired for an object in the cache by comparing lp_original_uri of the entry object that is constructed out of the response from the PATCH with the self_link of the object in the cache. Rev 14634 changed things so that the entry is constructed with the _new_ URI as lp_original_uri and so it doesn't match anything in the cache.
Some more poking suggests that rev 14634 broke this.
The code checks update events need to be fired for an object in the cache by comparing lp_original_uri of the entry object that is constructed out of the response from the PATCH with the self_link of the object in the cache. Rev 14634 changed things so that the entry is constructed with the _new_ URI as lp_original_uri and so it doesn't match anything in the cache.