Dear Gyula,
thanks a lot for your message. You understood correctly and provided the right solution: I just unscrew the four rear screens a little bit, and the device got working again as it did in the past. Great!.
Indeed, to store it I use a small metallic box and to protect its screen I put some foam around it, so that probably the foam was increasing the preassure over the screen, thereby leading to this "pressure effect" on the screen and blocking it.
Again, thank you so much!
73! C¨¦sar, EA5IOQ
Cesar, EA5IOQ