Have continual grounding problems. I've soldered and re-soldered. Is there a way to more scientifically check around maybe using a multimeter to find the source of the bad grounds?
All of your grounds should end up in one place: the ring of the output jack. Set your multimeter to ohms, put one probe on the ring of the jack, and the other on whatever you're grounding. If you have a solid connection the meter should read 0.