I use an app (Trilium Notes) that doesn't correctly map cmd-left/right-arrow to move to the start/end of line. It uses "home" and "end" instead. I mapped these in KM and limited the macros to that single application.
Now, if I have that app in the foreground and press Cmd-Tab to switch to another application, and if I use the arrow keys to move through the apps in the KM switcher, it thinks that Trilium Notes is still in the foreground and executes the macro, exiting the command switcher and passing Fn-left/right-arrow to whatever app happens to be next in the list.
I think this can be fixed by having KM recognize that the switcher is active instead of the previous application. I don't think there's any situation where I would start to use the app switcher and still want a keystroke/command mapped to the application that I was just using. Alternatively having a way to tell KM "Only trigger this macro if the keystroke right before it was not Cmd-Tab," but that seems like the wrong route.