Hp 41CX only displays something when pressed on

[Lode]

Hi,

I got an HP 41CX which appears as if it doesn't turn on, but it briefly works when firmly pressing downwards on it (when it's horizontal on a table).

This works the best when it's pressed at the bottom side of it, and less well when pressed on the display side.

It seems like a display problem, because when entering some number while it doesn't display anything, then pressing it, it shows the number entered earlier. In fact it even works when pressing the left and right bottom sides downwards gently at the same time.

Dear experts, any clues what could be wrong with it, and if there could be a safe way to repair it? I don't think it has ever been opened...

Thanks