I had this happen with the P51 I mentioned. Sounds like a Rx issue but could also be the Tx as well. I am not sure what Rx you have whether 2 Gig or standard but the older 72Mhz Futaba (as opposed to Hitec) particularly appeared to be shock sensitive meaning a few real hard landings might turn the RX flaky. You bring to mind another incident where I had an RX start to act wiggy. The plane rolled over left through some trees but I managed to recover it and land it.

I have had success with sending questionable units back to Hobby Services to be checked. If you ask them to flight test it I have been told they will but if I had to bet money on what happened here with you, it sounds like RX for sure.