I'm not sure I get what the heck is going on here.

The rear wheels of my walk-behind MTD mower turn on bolts with a 3/4" cap.
The (plastic rim) wheels have become loose, but I cannot tighten nor losen
that bolt. I can see it spinning in the plate as if the threads were
stripped. Neither clockwise nor counter-clockwise do anything.

Both rear wheel bolts behave this way. But the end of the bolt looks like
it was flared out a tiny amount so that it is perhaps some kind of
press-fit ??? My local repair place says that this is very unlikely, but
the mower is not worth bringing it to a repair shop.

Ideas?