The touch screens are resistive a plastic film over the top, I suspect that condensation is creeping in between the touch element part of the screen & the plastic membrane, I believe these are obsolete now due to ROSH compliance If I remember correctly some years ago we had one that somebody dug a knife into a number of places on the screen, the unit was EOL, however, we could buy another but the price was hiked up, we had no choice but I downloaded the application to keep as a backup, after replacing the screen (we also had problems with the touch screen not calibrated even though we calibrated it, this we thought was due to condensation as the factory was at 5 Deg C (food production), I took the old one apart & removed the touch element, found the original MFGR but they said it was obsolete and did not sell only to their distributors, they gave me the names of a few who may have some old stock, one of them had two in stock at £55.00 each I purchased both, fitted one I had to use some double sided tape but used some that was slightly thicker than the original, it worked fine & we changed it back, never had a problem again with condensation so assumed it must have had a bad seal. I very much doubt that these are still available. so although we paid nearly double (OEM supplied one with program already installed) than the original cost of a new one we at least had a spare plus a spare touch as well.