You're right again, setting beautification level to 0 fixed the preview issue. Thank you!
I have to say this ROM impresses me more and more. Battery life is better than when the phone was new - usually at the evening 40% - 50% remaining with 3 - 3,5 h SOT (I don't play games but read and watch a lot). I wouldn't believe if I haven't seen it with my own eyes.