dark band length of the plate

Hi i am new to this forum but badly need some help, the imagesetter i use is a agfa Avalon v4 or originally Palladio 2, with processes less plates which was installed in 2010, my boss decide not to have service contract so it is costing a fortune the problem is i am getting a dark band right a cross the length of the plate and when put on our press it looks bad a special on a flat tint, i have had the laser, the spinner , cylindrical lens the Mcon circuit board which is the big board, lens have been cleaned by me and agfa and a chap from screen , the processor is clean with new chemistry and new scrubber rollers the plates i use are agfa azura vi, i imaged a plate stopped the imagesetter turned the plate and the band is still the same but the other way because i turned the plate i have been in touch with litho supplies to see if they do the same plates but with the grain going in the opposite direction

thanks Raj