Is the finish using CA? If so that could be the cause, there is a spiderweb effect that happens under certain conditions and easy to avoid.
It can also be caused from buildup inside the tube such as glue, burrs and the like. When the parts are pressed in it expands the ends of the tube. You can either ream out the ends or pre-expand them and glue in the parts. Some kits are better than others for delicate blanks.
Also a photo helps greatly