I'm using XCR coating resin since last year. And never had difficulties to sand it dry. If it was hardened for at least two days, dry sanding always went smooth. But I've experienced the opposite this Summer. When it was impossible to dry sand resin that was hardened for 4-5 days. It clogs sandpaper or Abranet immediately. Also noticed weaker adhesion properties of that resin, no matter that previous coat was sanded with 220 paper. I have suspicion that it has a lot to do with air humidity. But maybe there are some additives available that would help to avoid such problems ?

That does not come easily, only with sandpaper. But only wet sanding possible. Or using kilometers of sandpaper. It looks like good glossy surface. But when touching it with fingers and holding finger longer, it feels a little bit sticky. And that does not come out even after two weeks of keeping in warm. Only mechanical removal is possible. Also I've noticed that covering another layer of hotcoat causes week adhesion if  that sticky layer previously is not removed but for instance only made mat.
So what factors else I should consider ?