So, I’ve faced very annoying problem: printer (samsung ml-1630) indicated that there is paper jam problem, but it’s not true in fact.
To solve this I’ve done a lot of stuff (all instructions from manual, inner cleaning, etc.), but nothing helped.
At the end I’ve finally solved the problem via opening the paper tray and clicking several times on white clickers at the end of tray on both side.
UP.: it also might help with paper jam (advice from comments)
Clean the the rubber that grip the paper out of the tray with some medical alcohol (70° is enough). They these rubbers apparently tend to catch some paper fibers or grease that could also make the printer think that it’s jammed.
UP. №2: also might help to blow using air-duster back side of printer. Before blowing take off back panel.