Vertical marks appearing on the neck that gradually continue to the notch line on the can. This occurs during the shaping of the neck.
Fix the necker station.
Low/high over varnish film weight or bad distribution on the neck.
Apply the over varnish between 3g/m2.
The over varnish is below the top end of the can, leaving excessive area unvarnished.
Check the over varnish unit.
Excessive layer of zirconium-aluminum phosphate in washing stage 4.
Check results of the washing stage 4 (muffle oven test).