I don't really think Traxxas would do anything about it, but it's worth a try. If not, then there are affordable radios with endpoint adjustments (Radiolink, Fly-Sky, Spektrum SLT3 from eBay, etc).
The problem most likely was always there, and you never really noticed it until now. It could also be that the dust, debris, and everything made the clicking worse, and thus more noticeable. Having that only happen to one side is pretty common, as the endpoints of the servo aren't always the...