Nothing ever moves when the tire is inflated. The pressure within ensures that by pressing everything firmly to the outside. But once the tire is flat, all is slack and stuff can slide around. Riding or even walking a bike with a flat tire can cause his problem.

I suspect that what he's seeing isn't the rim strip but the tube itself that once flat was worked under the bead of the tire and is peaking out. Pushing it back into place before inflating is necessary, but odds are there's a puncture someplace and it'll have to be patched.

There are lots of good tutorials on flat repair and tire mounting available on the internet, and there's even a few i-phone apps. I suggest that now that your son is in college, you cut the cord, and point him in a direction where he can get the help he needs for himself.