I've noticed a very brief flicker in any app window when I use the BTT hyperkey to send an "open URL" action to Keyboard Maestro. I see it particularly in the window's top toolbars, clickable items in inspector panes and in the window's drop shadow.
It doesn't happen with a BTT hyperkey that's not sending a URL to Keyboard Maestro.
Any idea what's causing this with BTT, or how to stop it? With clickable items flashing, could it have something to do with accessibility features?