CDJ800MK2 problem with MP3 (maybe audio-CD as well)

Hi there PioneerDJ forummers...

So I have a pair of CDJ800MK2, 2nd hand, 3 years ago. Been working fine, until about a month ago. Since then, it's stopped to properly reproduce MP3 files; the kickdrums have a faint ghost echo, and hihats sound outright bad (repeated or glitchy). Then I connected them to my studio speakers, and heard some odd noise in melodies as well, and listening to normal audio CDs, the hihats sound a bit distorted as well...

Does anyone know what this might be, and what the solution is?

Thanks!!!