That is typically a setting with the printer. There is garbage characters coming in from somewhere…. And ending up on the paper.
Tell the driver to rip the printer off the Velcro, flip the printer over and look for the #3 dip switch and switch that #3 to “ON”
Or… the little switch will be towards the center of the printer. The other 9 switches will be to the outside of the printer or “OFF”