Yeah it definitely sounds sensor related, just did a reset on mine (disconnected battery for 30 minutes, started and ran then disconnected for another minute) then drove perfectly. But I feel like it will probably happen again after a decent drive. Had to drive 200ks before it happens originally, but then it was continuous.
Probably a good idea to get Toyota to re-learn the transmission as well I reckon, as they all have the issue of not dropping into 6th early enough.