Dear Cristóbal,

Maybe it's OS problem. Check this :-

A couple of years back, Win3.11, Panasonic 3626, bits and pieces of the line being printed is "brought-forward" (or up), i.e. the words "HELLO WORLD" are filled with white dots, and the those missing pieces goes down.

Guess what, we changed the driver for the VGA card, and the problem disappeared.

Good Luck. Kenneth.