Dog-clutch hot squeak

Just got my gearbox from its 600hr rebuild/service by my Eastern Canada Rotax service centre, who reported that all the internals were good and within spec.  But now I have noticed that the Dog-clutch is squeaking when hot. When cold, and the crank is locked, it measures within spec, feels right, and makes no sound when rotating the prop back and forth through the dog's 15 or 30deg flat spot (can't remember which, but it's a current style clutch assembly).  But when the engine is hot I can hear a squeak at idle (when the dog is in play), and when the hot engine is stopped and the prop is moved by hand, the dog grabs and slides and groans... it's not smooth. It has about 20hrs on it since the rebuild, and noticed this issue around the 10hr mark. Once cooled, it is smooth and quiet again.

I would assume this performance is not good/acceptable, but I cannot understand what could have changed in the service/rebuild.

I always run the rotax spec'd aeroshell sport +4, and mogas (no ethonol).

The mag plug looked good, and nothing of concern was found in the oil filter.

Any advice/experience greatly appreciated.

Cheers, Pete