I would, with the keypad, slowly move the carriage over the spot where that keeps happening and look very closely. Move it around a bit you should easily be able to see what is going on. Like Modern Ink said I'll bet one of your crash guards is out of alignment. They both need to be exactly 1mm above your substrate. You can loosen the two small screws above them and use a long 1mm feeler gauge to adjust the height. Then screw them back down slowly a few turns on each screw then the other till tight. The 1mm feeler should then slide freely underneath the crash guard and then add a .10 mm feeler on top of the 1mm, it then should not pass, that should be it.