OK, you said they stripped the bolt. If they stripped the bolt, they could have chased the frame threads and that should have made it good with replacement of the same size new bolt.
Now if they stripped the frame threads, they should have put a HeliCoil insert or a E-Z LOK insert to repair the threads and without need of double nutting or any other
fix. If they tapped it, sounds like they went up one bolt size. That was taking a short cut!!! IMHO
I included a video of a HeliCoil insert process.
How to Install a HeliCoil