Thank you very much for your help.
So far I tried:
- changed head
- changed dampers
- changed filter in white circulation system.
- change ink, material just in case
- turned off white ink circulation
- changed white container (which has stirring)
The nozzle is not perfect even with new head, but it seems that for this particular problem it doesn't matter, sometimes the nozzlecheck is better but the problem is worse and vice versa - but I understand that there has to be some problem if the nozzle is not ok with new head.
The machine is about 7 months old and it was always running with no problems.
What I have not tried yet, is clean white tubes and change the feeder tank which is right before the dampers - could this help ? Should I do this ? And if yes how often ?
But, the problem is not constantly same, for example yesterday, in the morning it was almost good, just small amount of dots around, then it got much worse with a lot of dots, I tried one strong cleaning and one normal cleaning right after the strong one and then suddenly it was perfect 100% clean for the rest of the day, several hours of printing. Today almost perfect but not as yesterday, tried the same cleanings but it doesn't do much difference.