Here's my take on radio glitches. First of all, it is the worst thing to deal with on a race day. I battle radio problems with my M8 for almost 2 months. I even took it to Airtronics and they said all three of my receiver, 8 sets of crystals and radio have no problem. Took it to the track the next week, still glitch city.
The problem was simply the fact that my module was old. It was the original module that came with the radio when I bought it 2 years ago. After talking to some of the factory racers, the first thing they recommand is 27Mhz (I was on 75mhz), and the following are information I gather from them:
Futaba modules will go out anywhere from 6 months to a year
Airtronics is about 1 year to 1 1/2 year. And the other brands are about the same (those that use a module). Sometimes this is not a problem at certain tracks, but at tracks where there are a lot of interference (for example, metal fence around the track, florecent light over head...etc.) it can create severe interference. And the reason why Airtronics was not able to detect any problem is because when they are testing equipments, it is most likely in a "friendly" environment for the radios.
Simple solution is to just change the module. I switch to a 27mhz module, with a 27 mhz receiver on the same M8 radio system and had not had a hit since, even when I attended TCS in June where there was over 100 entires.
Other things that can cause glitching are blown capacitors on motors (espcially stock motors). Epic motors, which have surface mount capacitors can blow out, and you won't even know it. You can remove them, and install normal capacitors on them, and it should work fine. Also look into trying different receiver, crystals, and servo (servo glitches are rare, but it does happen), and speed controls. Make sure to change one thing at a time so you can utilize a process of elimination. Don't be surprised that sometimes it can be a combination of two things (seems to happen to me all the time
Lastly, make sure all your wiring is good, and your radio equipment is clean to began with (as in have it tuned on a regular basis).
Cars don't cause glitches, it will however, tell you how "clean" your radio equipment is
Hope that helped!