Keyboard shortcuts randomly don't work

Maybe 90% of my attempts to use keyboard shortcuts defined in System settings -> Keyboard -> Shortcuts fail. It doesn't seem to matter how long I hold down the key combination. They just work, or don't work, at random. More accurately, they work in short bursts, for a while, until they fail solid for a long time. I still haven't worked out what it is that I'm doing that makes them come back.

I've tried Super+Key, Ctrl+Alt+Key, Ctrl+Key, and Alt+Key. They're all very unreliable.

It kind of looks like the root cause is that the OS isn't trapping these keys low enough on the stack. It seems like there's a race condition with other apps that might want to claim part or all of the key combination. For example, it appears that Ctrl+F1 gets trapped by the Chromium browser, and overrides the OS setting. It's like, there's no sense of which agent owns the box.

Yes, I've read the threads on how to reset Gnome, etc. But I think there's a fundamental architecture problem here.

I could just give up and use the Super+1, Super+2, etc. provided by the Launcher. But they have problems: (1) high latency (how long can it possibly take to print a digit on top of an icon?) and (2) the refusal to launch more than a single instance of a single app at a time.