I had a 46 sized SU 31 that had a bad habit of rolling right made me nuts for about a week one day i was flying it pretty hard and neer where i was standing and it did this. To my surprize i heard a buzzing noise after several passes i herd i more and more every time i herd it it rolled right on the turn to final it did it at a much lower speed and i almost went into the weeds. when i landded it i found the covering had come loose on the leading edge. with no wind it laid flat on the wing and you couldnt see it even when powered up the prop wouldnt blow it back but when you pulled on the elevator in a turn or to climb out it would peal back and that disruption in the air flow would stall that wing. Ive seen other planes crash due to the seem being on on neer the leading edge check your covering iron it often.