Cdj 900 E-7022 cpu

I have a set of cdj 900s my cue button randomly stoped working the otherday witch i fault was weird coz ive just changed buttons an switches over. So i change the switch over again (resolder to bord) witch i have done loads of times before as it is so easy nw when i switch the deck on it comes up E-7022:panel cpu error it was working before just had no cue button so quite baffed to why this has come up wont let me do nuffin any1 have any ideas wat this could be an hw i sort it my first thought is it could be the play an cue bord were my decks are over 4 years old an have changed buttons a good few times