I’ve had a look at mine. I’m not sure I can be of much help.

Firstly, I’d try Loctite glue (Loctite 415, something like that). It adheres fiercely, my understanding of it is that it slightly melts the two pieces of plastic it’s sticking together to create a strong bond. Problem is you’d need the tiniest bit for that particular piece, and not sure how that would go if there’s already some glue residue there. And you get that stuff on your fingers and it can be strife. So not sure this is a good solution.

A much more tricky option is to create a new nub, maybe a pin with the end filed round and smooth, but that would involve drilling a hole in the engine part of the wing and it’s the kind of thing that’s desperately easy to screw up, and the outcome (if negative) can be irreversible. Not something to try if you’re not confident.

On my Ramjet, the friction of the pin that the wing pivots on is quite strong, so even if I cut the nubs off mine, I wouldn’t have an issue keeping it in place in both modes. If yours is loose, maybe you could solidify that joint a bit more with some (like, a tiny amount of) nail polish, dripped into the bit of the jet engine that forms the robot heel, right where the pin inserts. You drip it in and then move the joint around until it dries (a few minutes). It shouldn’t be visible unless you’re really looking for it, and will improve the friction of that pivot, so the nubs further along the wing become unnecessary.

Hope all that makes sense!