In Thailand, where the humidity and temperature are averagely higher than the US, this issue is very common.
I'm administrating a Facebook group called PRS Thailand that consists of thousands PRS owners in this country and I've seen so many old PRS affected with it. We even got a Dragon 2002 with entire body heavily covered with cloudy finish, as well as many HB II guitars. There's nothing we can do much to escape from this to happen - be it cased or standing outside the case. It would happen as the finish formula isn't designed to resist our environment.
Almost all of owners in Thailand solve this issue by sending their guitars to get refinished by local luthier because sending those PRS back to the factory cost up to $3000 - which is clearly not worth it considering the price of the guitars. In some local repaint shops you'll see many 20th Anniversary Customs, including some that belong to my friends, got sanded and laid around waiting for staining.
For US owners, the cloudy finish issue may sound weird and unbelievable that it exists, but this has been considered a serious problem and many people here are avoiding buying used PRS here becaus of it. It's simply not okay to pay for refinish job on a $3000+ guitar, oh, except the Dragon 2002 below.
PRS has been making great guitars since the start of business, but they takes 35 years to conclude that CAB finish probably be the way out of all issue like they once said when debut of V12 finish 9 years ago. Who knows what to see in the future...
Just adding some photos that were shared in my group for some evidences.