There may, indeed, be some sort of problem with the paper being fresh. JandC is certainly the expert with Eastern European photo products.
But, back in the days (1968) before RC paper was invented and we all printed on Kodak Medalist and DuPont Varilour, improperly hardened prints always used to stick to eachother and to the Arkay dryer apron.
This is what hardening fixer was invented to prevent by hardening emulsions.
Fixing was tricky in those days. Too little time in the fixer meant soft, sticky prints. Too much time in the fixer caused brittleness. Print emulsions would craze like the glaze on old pottery.
Temperature was not a factor. I once printed all night to get a portfolio ready for an art school judging. I dried the prints on an Arkay flat dryer and then piled them under a heavy weight to flatten. When I returned after class, that two-inch pile of prints had bonded into a solid brick. I had to reprint the whole thing.
Unless there has been some major improvement in the way fiber paper is made, I would still recommend a hardening fixer.