more info
Thanks for the input everyone.
The cuts are on the top of the right wing.
This was the third plane I covered with monokote, and has been restretched at least once. I'm sure I could have overstretched it to get rid of wrinkles, but I haven't had any of this type of problem on the other planes I've covered.
I guessed it would have to be caused by wing flexing as well. If it's just a question of repairing the cuts in the covering, that's easy enough. I was wondering whether I ought to be worried about this type of flexing. No one so far seems concerned about it. Should I be?