From my side, I think you can check all contacts between ink transfering rollers. Make sure that the contact is even between two sides (D.S and O.S) of rollers. If some of the inking rollers worn, I think you should try new one. My idea is based on your information I have talked above (waterless,...).
It would be better for anyone willing to help you if there is any photo!
rgds,
DeltaE