There weren't that many screws. I got it tested down to the train itself being the problem. I then started to dig into the underside and sure enough, there was some gunk built up on both trucks wheels (not the middle rail). Not sure when that happened, but I expect my girls were playing with it while I wasn't looking. Cleaning that off and it runs almost normally. I also cleaned the track again just to make sure. I'm wondering if there still isn't a problem with the train itself, as I still get an occasional flicker of the interior lights, though the static sounds are now completely gone. I'm going to clean the track and trucks again when I put it back together and hopefully it works through Christmas.
Thanks to everyone for the help.
