Re: BOLT head in the Bilge...
Sometimes simple is better. If you have a bit sticking through dremel a slot or an 'X' and take it out with a screw driver (of course penetrating oil etc.. first)
As others have said, I'd replace all of the bolts, but first I'd call the service who did the realignment and tell them they have some explaining to do, followed by a refund or repair. This didn't happen because they did the job right, not in a couple of months.
Lessons learned are opportunities earned.