increase/decrease stretch shortcut not working

Increase/decrease shortcut { and } do not work
I am on version 3.6.2 in Linux with Italian keyboard.

The shortcut is set to the custom curly brackets { and }.

In the shortcut customisation I can set the bracket and it is correctly recognised by the actual key combination for obtaining the curly brackets on an Italian keyboard ("Shift + Alt Gr + è" and "Shift + Alt Gr +plus sign"). In the shortcut picker the key combination is clearly recognised by { and } and not by the key combination.
When editing the score, however, the shortcut does not work.