Having trouble with my transponders not fitting tightly in the receivers. I have to switch between vehicles but the plug doesn't fit tight, I have had it come out on two different races and not count my laps. Anyone run into this issue?

My RC4 is a little loose in terms of fit in the Futaba rx I use but it has never pulled out and affected a race.

I have never had that issue. Maybe the plug/metal plugs are bad now from switching..

If you want to replace the plug with a fresh one, this is a good deal.
http://shop.awesomatixusa.com/parts/products-terry.html

Two things to think about. The fit of the metal male and female parts. The fit of the plastic plug and the rx case. If the plastic plug fit is too tight you risk pulling the rx case apart. I trim my plastic plugs to fit without hardly touching the case. I also check to see that the metal pins have a tight fit. You could also secure the wire in some fashion like a zip tie.