What happens when PLA gets damp?

I have been having some major problems printing in the last few weeks. I have a PRUSA i3 and it's been printing really well for just about 2 years now.

But now problems have started, its the same problem all the time, the PLA gets jammed in the extruder and when I pull out the bit that is jammed it looks all mashed up from the hob bolt and all the shavings are jammed up in the extruder.

I changed the hob bolt, same thing.

The odd thing is though some colours are worse than others, I have some clear PLA, nope this gets jammed very quick, some will go longer before jamming.

My only thought is the PLA roles I have all come from different places, some are quite old...

Could this be they are damp, the house is not damp but they are all stored on an open shelf, I have seen lots of posts about you should keep it in containers to stop it getting damp but I cant see anything on what happens to it when it does get damp.

I bet you checked this yourself but it sounds like there is to much pressure on the filament.

I dont think it would be moist, since your house isn't moisty.

My house is moisty, even my linear bearings are rusted on the outside because of this, i have filament of almost 3 years old laying around here opened, it still works fine.
With nylon it would be a problem, but that even has moist in it when you unpack it.

Does it jam in the extruder or in the hot end? and if it's in the hot end, you need to check if it jamms in the cold area or hot area.

The best thing to do is take your hot end apart, clean it, replace the liner(if it has one) and put a new nozzle on it. Then it will be like new, and you can eliminate that possibility. Hot ends are cheap to maintain.