Had some luck with a similar problem by inserting a couple of short lengths of -thin- electronic solder into the hole, then replacing the bolt in question. The trick was not to get over-enthusiastic about tightening. The assembly was still together when the car parted company with me (in fact, I'd forgotten all about it until reading this post).

Needless to say, not a good trick to use on more critical parts of the car, heh!

It's possible some other pliable metal might work better than solder.