Marcin, I know you mostly get complaints and requests for help here (including from me), so I wanted to take this opportunity to say THANK YOU to Zortrax.
I've been printing some really huge models lately - that fill the 200x200 bed, and require 8 pieces of that size to be assembled together. (It's a custom tube rack for a water bath shaker.)
Z-ABS worked OK except the prints kept peeling at the corners due to shrinkage.
I switched to Z-ULTRAT and the prints come out perfect every time. Great stuff, and reasonably priced.
I really like the way Zortrax approaches this business - make a reliable combination of hardware, software, and materials that "just works", without tinkering. And the materials are even reasonably priced, so I'm not tempted to waste time trying "other" materials. (But I like having the option all the same).
Keep it up and you'll have a steady customer in me. :-)
(BTW, judicious use of a heat gun can un-warp ABS prints. If you're careful.)
Have a great weekend.