The PX has a PC computer board in it with a battery. If the battery goes bad then all sorts of weird and wonderful (not) things can happen, up to and including not booting. I had this happen on my X32 rack mixer after leaving it at a mate's house for several months. I now turn on my PX for a couple of hours every three or four days, even if I don't intend to use it, just to keep the battery charged. Not sure if or how this could cause problems with the globals button but since you hadn't used yours for some time I thought I would mention it. Good luck.
Keith