Okay, good thing I haven't tried doing anything about the magnet yet.
In that case, my first thought would be one of the wires for the battery, maybe. The battery was dangling with the cover off, so the wire was definitely moved. I'll give it a try while I still have the amp at home.
When I recorded the video, I had the cover on and no problems, but I did have issues with the pedal tuner, sometimes (and every time before the day I shot the video) it would work perfectly fine, but that day and the following day, it would either show nothing or it would all be A's and B's no matter which string I played. I think the A and B thing is kind of like no signal going through though, because when the tuner is on and nothing's plugged in, it does the same thing.
Anyway, then I recorded the video and had no problems with the guitar through the amp that day. The next day I went to shoot a couple more angles and I plugged it in and it wouldn't work. If I unplugged it and plugged it back in enough, it usually did work, so I thought it was the jack. I unscrewed the jack plate and took out the jack and looked at it and checked if the wires were loose. Everything looked fine, so I put it back. I changed the battery just in case. I plugged it back in, it didn't work. I took the cover off, then plugged it back in and it did work, that time I was able to put the cover back on while it was still going through the amp, but later in the day, my brother was playing it and it wasn't working through the amp, he took the cover off while it was plugged in and it started working, put the cover back on and it cut out, took it back off and it worked again.
I know nothing about wiring, that's why I got EMGs.