I have had this same problem with mine, since the adapter jack is loose it's probably broken loose from the circuit board inside. I had to carefully dis-assemble and re-solder the adapter jack back to the circuit board. This is un-fortunately a weak point on some of Zoom's pedals, when you or if you get someone who is good at soldering to do it for you ask them to beef the solder joints up a little to help keep it from coming loose again. I re-did mine and I've never had another problem with it.