Thanks Pete for the reply.
Yet, my question was more specific: are there known issues with gears from specific years, etc. As it is already clear to me that I have to replace the gear, I need to be equipped with some knowledge to be able to monitor that the next gear will not be like the one I purchased a few months ago.
As the car is old, I don't want to invest too much money on the gear, so I have no intention to do it in Mazda's official garage. Most of the mechanics and even good ones do not know to tell exactly which version is suitable to which car (unless it is exactly the same model, which is rare when getting a gear from accidents).
Do you know where I can get information about the suitability of different gears to my car model? Do you know from which years Mazda used the same gear in Mazda 626?
Appreciated in any case.