The left flipper went dead on my Firepower. I took it apart and put it back together and bent the EOS switch a little, and got it to "sort of" work. It flips at about 3/4 strength, and when you hold the flipper button down it wobbles back and forth a little at the top of the flip. I noticed that if you then press the right flipper button at the same time, the wobbling gets much faster, which is what makes me think it's an electrical issue. Also, the machine has always had issues with things like needing to warm up (sometimes for 1/2 hour) before it will play a game, having to turn it on and off several times to get the displays to appear, and sometimes starting the first game without all the sounds. I tested the batteries and they're fine, although they are lithium batteries and the voltage is lower than what you'd get with regular batteries. The flippers have been rebuilt fairly recently and the right flipper has no problems.
One other thing that may or may be relevant- in order to get the left flipper to work at all, I have to leave the bolts a little loose so that there's some play. If I tighten them up, the mechanism pushes the metal rod into the coil at a little bit of an angle rather than straight in, and it doesn't work.
Any ideas about the flipper? Could it be related to the other electrical issues?