I would encourage you to open the synth up and and make sure there aren't any loose connections, maybe reseating any ribbons or chips you see. I just bought a "for parts not working" AN1X for about $200, and all I had to do to completely restore it to was pop in a new battery and heat up the solder on one of the assignable knobs.
All you have to do is rest the keyboard on a soft surface (I put a bunch of bubble wrap on my workbench) and unscrew all the screws on the bottom. They are all the same type screw so you can just toss them in a paper cup. The bottom panel lifts right off and is easy to put back on afterwards.