I have a SC HB1 with the piezo that I really like. However I'm having an intermittent vibration buzz coming from the electronics area in the body cavity. Applying pressure to the plate around the battery cover sometimes helps. I've removed the battery and unscrewed the plate to look inside but nothing appears to be loose. Has anyone run into this before? Any suggestions?

It's only noticeable while playing unplugged but it's a little annoying since this is how I usually practice with the family around.