The areas away from the flooding were all slightly cupped both before and after dehumidifying, so I'm guessing the wood was exposed to humidity (mudding or painting) after installation. It likely crowned slightly and the original company didn't let it acclimate before sanding it flat. Then when it eventually acclimated it would have cupped like that. It looks more pronounced in the video than it was.
Great job! The amount of attention to detail is wonderful! I hope we have more workers like you. Keep it up and wishing more success.
Figure out why it cupped in the first place?
The areas away from the flooding were all slightly cupped both before and after dehumidifying, so I'm guessing the wood was exposed to humidity (mudding or painting) after installation. It likely crowned slightly and the original company didn't let it acclimate before sanding it flat. Then when it eventually acclimated it would have cupped like that. It looks more pronounced in the video than it was.