Agreed. I even like to take the bolts out and run a tap through the holes followed by some good dry lube. I usually only have to do this once on a new bike and then the bolts are no problem for the life of the bike. These steps can really cut down on future frustrations from cross threading and thread galling that have plagued many DIY owners.I'd worry...but that's just me. Tells me that something is loose or broken...both bad things in that area.
My next step would be to remove seat (sorry) and insert the "spinning bolt" and see what is really going without the seat blocking your view.
Then figure out how to fix.
I'd remove the single bolt and inspect the threads. Also, an awl helps to line the seat bolts up. Unless you have a custom seat that requires special bolts, the best bolts are OEM. Other bolts are made of metal that is more likely to seize, or they have sharp tips that can grab and damage seat material.
If you see nothing wrong with the bolt, and with an awl and flash light your hole lines up, the next thing to do is to remove the seat and inspect the threads. Possibly the threads in the frame are damaged.
I also use #2 Phillips screw drivers to align the 4 holes before installing the handles and bolts. Never had a problemI use a #2 phillips screwdriver to align the bolts. The tapered end helps center the holes. Also, do not tight any of the bolts until they are all in place. It's odd that three of the bolts tighten and not the fourth.
If the hole is stripped in can be fixed with a Timesert threaded insert.