Yeah, a good GC is either so astronomically expensive you can't even talk to their lawyer's cat, or simply not to be found (or you marry one or into the family).
I would get legal involved sooner rather than later; but a good lawyer can be as hard to find as a good GC.
Maybe you should just get the roof fixed and sell the house and try again.
Real talk, if it isn't obvious foundation damage and the roof isn't currently on fire, it'll probably sell just fine.
You can hire a home inspector after it's "fixed" and see what he says. Just disclose that you have solar and that you had an issue and it was resolved, provide paperwork, and most people will yawn.
When buying houses, I've really only hired them because I don't want to get on a roof myself if I don't have to :-) Or crawl around in an attic, for that matter.
Most folks are pretty bad at spotting problems with houses, because they simply don't know what to look for (and why would they? It's hard to know everything), so an inspector's probably a good idea.
Me, I spend the entire time at an AirBnB distracted by noticing every single place work wasn't done quite right, every cut corner or lazy shortcut, every interesting (or "interesting") material choice, "oh, looks like they replaced this shower insert but didn't want to fully redo the drywall so took the lazy route and added trim", "uh oh, this tile shower floor has serious drainage problems", "interesting, this doorway must have been added", et c., but most people aren't like that.
I would get legal involved sooner rather than later; but a good lawyer can be as hard to find as a good GC.
Maybe you should just get the roof fixed and sell the house and try again.