That's interesting. I bet there is a splinter of wood, blob of glue or something else down in that hole. It is also possibly that the wing just got assembled with a pocket that is too short. If you do end up having to cut the rod, it isnt the end of the world. like I said, I've had to do it on several planes. I think that the joiner tubes ore often just rough cut to the general size and require some fine tuning.