Laserjet4 - display ghosting?

My LJ4 sometimes repeats the last character on the control panel's VF display - e.g. just now when I turned it on it said "warming upp". The repeated letter (and sometimes it's repeated just once, other times more than once) always seems to be fainter than the regular letters. Has anyone ever seen this fault before? It's no big problem*, I'm just curious as to what the cause might be. I think it only ever does it during the startup sequence, but not during normal operation, which maybe suggests it's heat-related and "fixes" itself after the printer's been on for a little while. * if it's something such as a ROM going bad then it might become more serious - although the fact that the repeated chars are dimmer than the normal ones suggests to me that it's a problem somewhere in the display output stage rather than core logic. cheers Jules