Hi Everyone.
Mario I have never had a Psr series or any Yamaha Keyboards cause I never fancied them so what I am about to say is 100 neutral.
What happend to you is very COMMON especially people like us who gig a lot. I have changed quite a few on GEM WK serious at times I had to change the whole keyboard.
One thing I would like to tell you 1. is when you replace. If your keyboard have AFTERTOUCH be careful not to trun it over cause you have 2 ROWS of them CARBON pads, if you put it in a different direction you have to reopen and turn it the other way.
2. if most of you haven't experience it every now and then check all the notes and see if any of them sounds higher than the others, in that case it means that it is about to go.and one other thing most of them pads match with other makes for example roland puds are the same as WK4.

Good luck