seat bolt issue

So I had an amp installed and the shop didn't tighten down, or cross threaded one of my seat bolts. There's a 1/8" gap between bracket and head. The bolt will turn but will not get any tighter or looser. Is the nut welded under the carpet to the body. Should I cut the bolt and try and push it through? Suggestions.

 

The "female" hole is threaded ... goes all the way through ... in the floor. Just this week I had soundproofed my floor ... when replacing the seats one of the bolts did exactly as you described ... I had a bolt "slightly" larger the OEM size ... kind of self tapped itself ... now it's tight.

 

Thanks jp

 

They have the seat bolts at Ace hardware.
I replaced one when I did the bench seat washer mod.
And yes two of the bolts cross threaded and one we saved by cutting the end off and a file.

 

The welded nut broke off on mind so I'm not able to bolt it down. Any suggestions on what to do

 

1st the installers should make it right, but I wouldn't trust them.
Second option is a pair of vise grips locked on the head and pull up white removing bolt.
3rd option is to leave as is.
Pushing it through is, " I don't see how you could make that happen. "
Well, is it the drivers side or passengers side? Front seat or rear ?
I have a bench seat with the drivers front bolt that was screwed up and that was never going to fly!