This conversation has been merged. Please reference the main conversation: Photoshop CC 2018: Shortcuts using Alt key aren't working correctly (e.g. Alt-Backspace)
Now if you hold the alt key, it focus on the application menus (File, edit, ...) instead of listening for the rest of the shortcut. So if you want to use any alt related shortcuts, you need to hit the rest of the keys twice without letting go of alt - once to clear the focus on the menus, the second one for the shortcut to actually work.
Related and very popular shorts disrupted by this change are ctrl+alt+Z, or alt+backspace (and alt+shift+Backspace).
If you start the shortcut with ctrl, alt behaves properly; It you start the shortcut with alt, the problem occurs. Setting commands to wacom tablet's shortcut keys also seems to be triggering the bad key behaviour and breaking a lot of setups out there.