Ok. I have spent sometime at christmas looking at just this. I have discovered that the current budgie desktop print screen implementation is fundamentally flawed.
In layman’s terms you have two bits of budgie fighting over who is controlling and managing the print screen button and other key combinations. One is gnome-settings-daemon and one is budgie-window-manager.
Who wins depends on your computer. Some people have all or most key combinations. Some have few or none.
Basically this whole area needs to be rewritten either to comply with gnome-settings-daemon requirements … or to drop gnome-settings-daemon completely and manage every bit of device management by budgie itself. Both are big bits of work … the latter is the budgie v11 approach.
Whether there is a third way needs to be investigated further. Let’s see.