IPC PX-39A, on screen keypad not working correctly

Hello,

I am having troubles with the on screen keypad on a IPC PX-39A: when I want to hit, for example, button “7” the keypad reacts with ESC or ENTER. In other words, I hit with my finger a button but another one reacts (usually another one at the bottom right).

All the other on screen objects (pushbuttons or I/O fields) react correctly. Just the keypad is not ok.