Sounds like its just getting old, or electromigration, where the electrons have simply worn away the silicon or even the connects over time. Also, possibly a heat issue as well, making for underpowered scenario, as the heat goes up, the voltage goes down.
Try cleaning it if you can get to it.
If its bad when only in usage, then it could be a mechanical issue as well, as over time, and sooner as well, mechanical systems break down and wear out
I will clean it and see if that helps if not time to join the 21st century - Thanks