The problem is likely something wrong in the transmitter that's causing it to send inconsistent outputs. There's a chance someone is operating an amateur radio near you but it's not as likely as it was 20 years ago lol. If the problem just appeared out of nowhere I'd bet though that it's something wrong in the transmitter. It probably glitches internally just enough to let the ESC arm and you really see it freak out once it does.

For the 2.4GHz upgrade, if you have a local hobby shop that's really your best bet to shop for them since you can hold the radios in your hand and feel the quality. The Traxxas 2.4GHz systems are available with a trade-in from your current system whether it's functional or not. They do work pretty well but are a pain to program. They don't have an LCD display so you have to watch lights flash and move knobs rather than changing numerical values.

Personally, I like the Airtronics and Futaba systems but Spektrum has a couple lower-end entry level models now as well. Airtronics and Futaba are likely to have the best reception range where Spektrum doesn't go quite as far. I've only been able to run Spektrum out of range a couple times though and I was actually trying so it's not a big deal.

-Eric