So we closed in our carport and made a bedroom. Hired a reputable guy who we had used for other stuff in the past.
The carport had vinyl siding on the walls, he took that off and underneath was tongue and groove pine siding (smooth finish to the planks, not like knotty pine). Under that is tar paper then 1x6 planks on a 45 then studs. This was on 3 walls. Drywall went over top of t&g. The ceiling has plywood on it and he went over top of that with drywall. He used 3/8 for walls and 1/4 on ceiling. Built one new wall where carport opening was.
Job looked fine until we put primer on the drywall, and then we saw cracks in the joints. Nearly every one of them. Called, he comes back and spreads some lightweight filler, sands, says it should be fine. Said he called a guy who does this stuff every day and he said that it's probably a moisture problem and to use this particular stuff and it will be fine. Wrong. Next day cracks were back. We call an insurance guy we know who brings a moisture meter to test. Dry as can be. Called a local builder who asked a few questions and said it's the mesh drywall tape. Said it's crap and should only be used for repair work.
Called the guy, he comes back and cuts out every joint in the room, removes the mesh tape and goes with paper. That was finished 8/20. Cracks came back.

Only this time the cracks are
beside the joints. Not the joints themselves. Call the guy back and he comes in a tapes over the cracks, more mud. That was 6 days ago and no cracks. But now the ceiling is pretty wavy. The seams are much higher than the rest of the panels and it looks awful. And my wife is not happy. The walls are also looking humpy at the seams. Is there a way to fix all of this other than skimming the entire thing or ripping it all out ans starting over? We are just frustrated with the whole job at this point. We also don't have the funds to hire it out again and if it needs to be redone it will be yours truly doing it all by myself. Which I should've done in the first place but we were in a bit of a hurry to get in the room. And we still aren't.
Weird part is the new wall cracked too, not just the existing construction that he went over with drywall. This house was built in 68 so I doubt there is any settling left to do. House is SOLID built.