He's adorable! Yes, the flipping was almost certainly stress from the tank change. What/how much/how often are you feeding him? And are you using calcium/d3 and a multivitamin?
I had always thought that flipping, rolling and spactic movements of the limbs was a result of toxing out, not simple stress.
Before changing terrariums, how often in the four months that you had him was the substrate changed?