The most likely cause would be a loose blanket, or incorrect blanket packing. Retighten the blanket with a torque wrench; do not over tighten the blanket. Contact the blanket manufacture for their torque recommendations for your blanket and press. Torque wrenches measure either inch pounds, or foot pounds, most blankets are torqued to inch pounds. Over packing or under packing the blanket cylinder changes the diameter of the cylinder resulting in a different surface speed from the plate cylinder. The blanket will slip and create the slur. Pack the plate and blanket to the press manufacture's recommendation for the type of blanket you are using. On press verify that the plate and blanket are packed correctly with a packing gauge. In this situation the blanket was significantly over packed.
U.S. International Trade Commission Approves Tariffs Targeting Aluminum Lithographic Printing Plates from China and Japan
On October 22, 2024, the U.S. International Trade Commission (USITC) determined that a U.S. industry is materially injured by imports of aluminum lithographic printing plates from China and Japan. The U.S. Department of Commerce determined that the printing plates are being sold at less than fair value and subsidized by the government of the People’s Republic of China.