RE: Servo Twitching Problem
if you get some metal to metal contact on the motor (which you obviously do), especially parts that are not lubed, they can make some interference, that may have something to do with it. Try moving the antenna and the lead wires to the servo's away from the motor and power lines from the battery and such. You can also try lubing up some spots on the motor that could be likely. Usually for it to cause interference you have to be running a ppm Tx, and if you switch to PCM or DSM then you should be fine, although I'm sure those are not entirely failsafe either.
I suppose it could also be some type of vibration, but that seems a little less likely because you've got foam under the servo's and it's still doing it. You'd probably have to have a pretty good vibration to cause something like this, and the servo's would have to be cotnrolling a big enough surface that it could give feedback to the servo based on the vibration.
Maybe that will help a bit, or atleast get you started, good luck =)