Looks like U/V fail to me from either cheap clear without adequate protection or just not enough film build. Yea, you're gonna have to take it all off down to the factory finish or the primer in spots where they repaired.
I'd get a cheap compressor, a decent D/A sander (fine sanding pattern/finish DA) and a couple rolls of 150 and 320 grit paper.
First take a new razor blade and holding it almost flat see how much you can get off with that on the big flat areas. Be careful not to let the blade catch and dig into the surface.
Take the sander and 150 grit, keep it flat as possible and basically try and just take off 80% of the top layer of paint. (just the clearcoat) I usually try and do a 15x15 area then move on to the next area. Don't focus on the edge, try and take the whole section down evenly. .instead of just doing a little spot then a little spot It's easier to keep it flat doing a bigger section all at once.
Once the whole panel is done switch to the 320 grit and take off the remaining 20% and the basecoat. be as careful as possible not to get into any repaired areas, if you see primer and it looks stable, leave it alone.
Talk to your painter and see if he would prefer to prime and final sand it and how much extra that would be. We hate when people bring something in already primed and the customers saying "It's ready for paint" 9 times out of 10 it's not, and the paintjob looks like shit if we just shoot it. (of course it's the paints fault then, not the poor bodywork says the customer).