I had my ultrex do that exact same thing when it was a couple months old, took it to Sartin Marine and Brian replaced the armature (it had a bad spot on it) and its been gold ever since.. Took him about 30 minutes..
THIS! I had the exact same issue. Brian Sartin told me it happens from time to time if you hit a stump doing Mach 2 which I had done. As mentioned, it was a simple and quick fix.
For the auto pilot thing, are you sure you're not hitting the N button which turns the boat immediately north? I've done that a few times and it's been a couple close calls. LIke the other poster said I adjusted the speed on that.