My spider jam does the same thing. It's doing it right now. It's out of warranty. I tried to fix it myself . I am guessing it is a loose ground or cracked PC board trace. I took it apart a few years ago and applied some silicon rubber to several parts to hold them in place. This actually solved the problem for a few days but the problem came back. I like the amp and will take it to a shop and have a tech deal with it now. Frustrating.