George, thankfully it wasn't mine [X(] but is really sad to see nonetheless as I know how much the owner was looking forward to the model/doing this scheme!!

Personally, I think the model is flying too fast for any sort of tip stall and the pull out looks fine for it not to be a high speed stall. I if I had to make a guess I would say one side of the elevators or flap failed and returned to neutral resulting is an slow type aileron roll. The roll rate looked slower than an 'aileron' roll and slightly 'barrelly' which would support that thinking???

What servos/linkages were used on the elevators/flaps?

Rgds,
Mark