I still think it's the motor alignment. A straight-ahead motor makes the plane turn left. You need right thrust, and most trainers have about 5 degrees right.
ARF trainers like this one have a clamp-type motor mount that lets you re-aim the motor in a few seconds. It'll take longer to double-check and possibly readjust the throttle than it does to tweak motor alignment.

A buddy of mine has a plane that acts squirrely at full power. He has wash-in in one wing. It can be trimmed for flight, but if you change the throttle setting the trim changes. Makes for hairy takeoffs.