It’s an overlooked quirk of the list view itself, which has already been discussed in a previous thread:
Essentially, the lists have a few hard-coded shortcuts such as Ctrl+A to select all, Ctrl+D to select none, Shift+Up/Down to make multi-selections, etc.
In the meantime, if you simply reassign Duplicate to another shortcut that does not clash with the hard-coded ones, then it will work fine.