Slurring is the filling in of halftones and at the back edges of solids. Mostly occurs on coated papers and is caused mainly by paper slippage in the impression nip between plate and blanket or blanket and paper.

Doubling is a register problem that mainly occurs between plate and blanket within the unit.

Too much blanket to paper pressure. Reduce printing pressure to a minimum.
Too much plate to blanket pressure. Reduce plate to blanket pressure, usually 0.002 inches(0.05 millimeters) is sufficient.
Running too much ink, which acts as a lubricant that aggravates the slippage. Reduce ink feed, if density becomes too light, reduce water settings also.
Ink too thin. Increase body of ink. Consult ink supplier.
Piling of paper coating on image areas. Switch to a more moisture resistant stock. Consult paper supplier.
Blanket is packing is incorrect, packed too high causing a difference in circumference and intermittent register shifts. Lower the packing on blanket, and increase packing on plate. Check bearer pressure and reset if necessary.
Excessive play in bearings or gears of cylinders. Check and replace worn parts.
Web is being distorted slightly due to slack or tight edges, causing a weave in the web. Protect paper from changes in relative humidity. Make sure paper rolls are free from soft spots.