This problem may be caused while, if removing the Sheet Feeder, the operator rocks the assembly back and forth to eject it from the printer. This puts pressure on the platen hold-down bracket, bending it in such a way that the platen is loose enough to rise out of the frame assembly. The print head then does not firing squarely on the platen.
There are three remedies for this problem:
1. Remove and straighten the bent mounting bracket, then re-install it.
2. Remove the bent mounting bracket and replace it with a new part (# 076-0200)
3. Remove and straighten the bent mounting bracket. Drill out the dimple (the raised steel stamping) on the mounting bracket with a power drill and a 3mm bit. You can then mount the bracket with two screws instead of one. Use a SMW 2.6 x 6 screw along with a nut and toothed washer.