Is anyone else having their display freak out when the “display large text” box pops up? My iMac just isn’t having it. The script pauses and shows that message box until a condition is met, but every time it pops up as of late my display starts flickering really badly until I reboot.
I haven’t tested your particular case (well, you didn’t deliver any example either), but two weeks or so ago I played with a “large display” notification and I hadn’t any display issues on my MBP. (You aren’t on Catalina Beta, right?)
So, – I might be wrong – this smells like a more generic computer problem. “Generic” in the sense that it isn’t directly related to KM: The issue appears because KM is triggering it (not causing it).
I might be wrong here, as I’m wrong quite frequently.
But, to exclude this, you can do one thing. I call it “The three basic steps of Mac troubleshooting”
The first two things are pretty straight forward and will cost you 5 minutes.
The Safe Mode Boot needs some explanation:
Safe Mode Boot has two purposes:
Once booted into safe mode, all third-party components (drivers, kexts, login items) are disabled. This allows you to find out, if your issue is related to some other component of your setup, or if it persists also without any third-party stuff.
Test if your issue is replicable in safe mode!
Note: Booting into safe mode will take considerably more time than booting into normal mode, and while in safe mode your Mac’s performance isn’t like anything you are used to.
Besides that, safe mode boot also has two “side effects”:
The computer does a disk check/repair (fsck *)
It deletes many system and other caches. (In my experience, it is not unusual that issues are related to caches.)
These two particular effects of safe mode (the disk repair and the cache cleaning) will also persist after the safe boot (when you’re back in normal mode). Many problems are solved just by booting once into safe mode, and then immediately rebooting into normal mode.
Try out the 3 points, and let us know.
A flickering screen sounds like a hardware issue.
My guess would be that the large text window is triggering a GPU mode or turning on a GPU or some such, which is then staying on, and that mode/hardware is broken.
If your Mac is still under warranty, I would go get it replaced. Nothing Keyboard Maestro can do should cause the screen to flicker, and if it can actively cause the screen to flicker, then you have a reproducible case to get fixed more easily.