I'm having some weird flickering probs with my PD Mule. The flickering starts after 20 seconds or so, but only on the low level. It is intermittent, not really severe. It doesn't happen on high level, which makes me think this isn't a dirty contact problem. Have there been any issues with the electronics that could cause something like this? Any other ideas? Of course I should also clean all the contacts (haven't done that yet).