My MX-3 system is probably over a year old, maybe coming up on two.......can't remember. But anyway, it's still doing good, I doubt the transmitter is the problem, I'd more suspect the receiver of causing problems.

EDIT: Just took a trip out to the garage and counted the teeth on the pinion after I pulled it out.......turns out the current gearing is 16/49. Not sure, but just from what I've heard, that sounds a bit high........could that be to blame for the weirdness?