This is a gremlin that I've seen, too. Extremely frustrating. Even with passive bass, so battery was not my issue. Short of sending it in for repair/replacement, here are a couple of things you can try.Have read that the effects jacks on the back could possibly develop a bad/dirty connection on their normally closed contacts and that jamming a 1/4 plug in and out of each jack a few times could clean those contacts. That one makes some sense to me. But a couple of months ago, when the problem manifest it's ugly head, in frustration I tried a FACTORY RESET. Shouldn't have fixed anything, but I have not had a problem since. Let us know how it all goes with you.