Plates become sensitive during the run, and will start to transfer ink in the non-image area.

Improper fountain solution mix Check fountain solution mix for proper conductivity and pH, adjust according to manufacturer’s specifications.
Water and/or ink settings are too high emulsifying the ink Reduce ink and waters settings
Contaminated press mix Rebatch fountain solution chemistry.
Temperatures of fountain solution and ink vibrators are too high. Check temperature of fountain solution and ink vibrators, adjust to recommended specifications.
Ink not formulated properly. Consult ink manufacturer.
Plate non-image area becomes contaminated. Stop press and clean plate with a recommended plate cleaner. Can use a cleaner designed to be used while running for web applications.
Paper stock fillers such as calcium carbonate cause non-image area to become sensitive. Consult paper supplier, consult chemistry supplier for a fountain solution that has additives to combat this. Utilize a cleaner for calcium.
Press roller settings are incorrect. Check roller stripes to make sure settings are correct. Adjust to manufacturers specifications.