Issue with magenta color on RAPIDA 74

Dear,
since some time I struggling with issue as describe on the attached photo... half of the solid is light and second half is dark, so on normal job not solid there is small visibla mark always in the same place – middle of the sheets. I checked dampening system and it seems to be ok. It always occurs on first 3-4 sheets, rest are ok...
What could cause such issue?
Maybe someone had similar case...
thanks a lot in advance for your support...

 

Check your ink forms to the plate. and ink forms to your oscillator rollers. If its only the first few sheets that's normal.

 

are you looking to sell every sheet? Only kidding.... if all your throwing away on startup is 3 to 4 sheets Id say you're doing ok.