Touchscreen tills are often made using laptop parts and run Windows which means that their servicing and repair is quite similar to laptops.
This particular EPOS unit was crashing with a “blue screen of death” and had a faulty touchscreen.
We diagnosed the hardware fault as a failing stick of RAM which we replaced.
The screen itself was taken apart and carefully cleaned before being put back together but sadly this wasn’t to fix the problem.
Still, this is just a laptop in a different case so as a temporary fix we supplied an optical mouse which allowed the client to continue using their till.
Update: After a few days the touchscreen came back to life! We put this down to slight moisture left from the cleaning process evaporating.