Digital BW, The Print

Yesterday I noticed that I have got some fine detail banding in the
prints. It's like subtle white lines most visible in middle grey areas
like skintones. It's not visible in black areas or the lightest
highlights.
 
Nozzles are OK and I have preformed head alignment the best I could but
there is no difference. I am using PiezoTones and CIS - no apparent
trouble with CIS. 
 
What should I do now?
 
Notice: I am cross posting this in the [piezography3000 group] too.


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