Thanks for the hints.
Yesterday I logged in, played a few hands and the problem was still there. So I closed PokerStars Client and h2n, moved logs folder somewhere else, launched poker soft and the tracker again and... everything worked fine... no idea why - I'll keep an eye on it and be sure I will keep you updated.
The only thing I've done differently than usual is that I played a few Spin&Go games before moving to cash games.
I still have the old logs folder, so if you want it, I can send it to you.