Yashicamat 124G film winding issue

Hi everybody

I have owned a Yashicamat 124G for a few months - a great tool overall. The camera worked fine when I purchased it however due to a hazy/mouldy taking lens I decided to send it for CLA. Mark Hama seems to be well known as a repair technician for this kind of camera so it went there. My experience with him was not so great for many reasons (not relevant here). However, he did indeed clean the lens, which is now perfect. Sadly though, I now have issues with the winding mechanism that I didn't have before.

Essentially, the problem is that the camera believes there is a 220 roll in it even when there is a 120 one loaded. When I get to the last frame (12), and press the shutter button to shoot the last picture, winding the crank takes me to an (non existent) 13 frame and locks again. It wasn't like this before: the crank would spin freely until I felt no more resistance and could unload the roll. Now, the only way to unload the roll is to continue winding the crank, cocking the shutter and firing a series of imaginary shots from frame 13 to frame 24. When frame 24 is reached, the crank will then spin freely allowing me to unload the film.

Any idea what could cause this? Is it solvable?

Some additional info:

-the film plate is correctly set to 12 exposures, not 24

-the small window on the right side of the camera correctly shows 12ex, not 24ex.

Thanks for any help!