Sounds like it's extremely undercooked, whack it on the head and stick it back in the fryer for a while longer. Jokes aside, have you opened it up to see if any connections have started to come loose? Poor soldering at some of the joints can have a lot of wacky effects on a pedal.
I've had this happen with some pedals. Most often, it was simply a loose jack. Tighten them up and see if that fixes it. Beyond that, if the pedal didn't get fried by a power surge, it's a loose or bad connection inside the pedal.
Could be power supply / pedal chain order related. Also try the internal buffer / true bypass switch and see if that makes a difference. It could also be a faulty charge pump IC - which is a pain in the ass to replace. I've had to do a few.