Can´t assign some keys to shortcuts

I guess this appeared in last version because I didn´t have problems before:
I had set ctrl+D to a shortcut but when hitting it I get a duplication action.
If some key combinations can´t be assigned to whatever I want they shouldn´t be available in Actions and shorcuts.

Tricky one. I think it should be such that when a shortcut such as Ctrl/D was assigned by the user already, the according edit action (Duplicate) should not have any shortcut assigned whatsoever, it will then be up to the user to assign another one.