Originally Posted by
pw66
Have you tried using a piece of paper from a newly opened pack, to see if damp paper is the problem?
The coating on sublimation paper soaks up moisture much quicker than other papers. Now that the weather is slightly warmer and damper any reduction in your heating could be enough for opened packs to suck up any moisture in the air.
I always store my opened packs in a ziplock bag, with one of those poundshop 'dehumidifier' silicon packs in the bag.