@denyou I just got this working with @sleve_mcdichael's help on reddit. See if there's anything in that thread that helps or drop back in and I'll try to walk you through it here. It works like a charm and is a really great feature.
I had been doing all of my testing on an x86 platform. Since moving the scripts/overlays to my RPI4, I had to increase the sleep outside the loop to 2 otherwise it wouldn't pause.
I have similar problem. I thought its my adapter to the monitor. I use a dongle for keyboard too. What was the interval when you got this screen freeze? I get it maybe once in a hour. Maybe its a different story on my side.