My 1984 BB2000 is having an issue which I've already tried to address with my guitar tech. The issue is that while I'm playing with both pickups on, it will switch to only the bridge pickup without me moving the switch. Then if I switch to only neck pickup it has little to no signal. The tech installed a new switch and re soldered the wires and of course it's still happening. Here is a video of an example: Can anybody give me any suggestions on how to fix this issue?