RE: Source of Radio Glitches???
Crystal sounds like a good bet to me! Do the servos jump when you tap the Rx case? Over-voltage of the battery could be an issue with a fresh charge but should be OK after a few minutes of on time - some Rx's are more bothered than others. You might try a voltage regulator if you want to stick with the high capacity Rx pack. Easy enough to change to a 4.8V pack to check. If glitches are only with engine on, look for possible metal-to-metal contact (as well as crystal). Try unplugging your servo leads one at a time to see if there is an issue with one or more of the servos or servo extensions. Try a different antenna routing- it may help, depending what's close by. I don't know much about digital servos so I can't be any help there. I think you have most of the bases covered but I'm sure there are things I haven't considered. Good luck with it.
Ross