The local dealership here has been having problems with the regulation of brand new uprights (Yamaha and other brands). The reason we're given is that the factory is so behind that they're trying to get pianos out as fast as possible. Thankfully the dealer here is trying to prep the pianos as best as they can, but it's still an issue. So far we've caught everything problematic in the store before it gets delivered.
As far as the issues you describe go, I would imagine it's probably a combination between humidity and regulation.
New, not sure. But used? I'd look first to see if the spring threads are breaking.