Start with easy ones first.
Ctrl-Alt-Del is a ‘last resort’. Do not use it to exit any program unless there is no other choice or the program is running amok.
There is a Close/Quit gadget in the upper right corner of the main Gramps window. The Quit Gramps hotkey keybinding is Ctrl-Q or Alt-F4. Closing this way will cause Gramps to cleanly exit. That will close the database & unlock it before shutting down. Plus, if your Preferences have been set to backup upon exit, it will do so, creating the equivalent of a Restore Point.