Special tip, especially for all those "hyper-key" folks out there, but good for everyone to know…
I tried to assign command+shift+option+control+period as "Cancel All Macros" for Keyboard Maestro, and couldn't get it to work.
I didn't get an error or a system beep, it just appeared as if nothing had happened. But something was happening in the background, it just took several minutes before it became apparent.
Turns out that command+shift+option+control+period is a macOS reserved shortcut which will produce a "sysdiagnose" file in /private/var/tmp/ (mine was 350MB, compressed).
As far as I can tell there is no way to override or re-define that keyboard shortcut.