I can't work out what'r going on here, it's really frustrating. I'm trying to trigger MK actions in safari from hot key triggers. But if the shortcut I want to use includes the Control key KM won't work. Safari just shows a little text window at the bottom left of the window saying "Display a menu". It appears any time Control is held down and KM won't trigger the macros.
Using different shortcuts isn't really an option as I'm trying to configure context aware behaviours for a simple macro pad. I've set it up to use key combinations on each of the buttons that are very unlikely to be in use in any application (mostly all modifiers down). Then in KM I am setting up behavior for those shortcuts in groups that are active per application. So the shortcuts I use to trigger things in Safari are global. But as soon as the control key goes down Safari seems to block KM from working.
The weird thing is it does sometimes work for a brief while just after Safari has been opened, but then after a few minutes it seems to stop KM again.
Safari (and WebKit in general) hijacks the Control key for right-click/context menu behavior. I am guessing that it sometimes works because of where your mouse cursoer is but maybe not. I do have some Ultra Claw (Command+Option+Control+Shift (⌘⌥⌃⇧)) + triggers that work just fine for me when Safari is in focus so perhaps there is some other things happening like some other software. Have you closed out of all your background applications in the menus. In Activity Monitor > View you can see "My Process." That might give you a clue if something else is causing conflicts.
I think it also intercepts the combination of CTRL+OPT, I think. He said "mostly all modifiers down" which tells us that he's using the OPT key at the same time as CTRL. That could be the problem.
It should still work -- most of my Safari hot key triggers are Ctrl-something and they work fine, despite that little message appearing. That's on macOS 15.1.1, 15.3.x and 15.4
Is there any connection between the sites the problem happens on? Do you have any extensions that might be getting in the way? Have you tried KM's Interactive Help -- Something expected is not happening...?