background lines

I have an older AL model that was recently overhauled at Carvewright. Lately it has been having an issue with lines in the carve region but not on the pattern that I have placed in said region. The pattern figure comes through very well, no lines. I will attempt to add a picture. Any thoughts?No luck on the picture, but the lines are about 1/16 wide and are vertical and randomly spaced maybe 1/8" apart and very shallow but obvious.

I would check the Y and Z bearings especially the Y. It could be bad bearings or just a case of the bearings need adjusting. It could also be the little bearings in the Y gearbox and worst case the shaft is worn. Do a search for Y gearbox bearings and there is lots of info.