Good suggestion. I tried that, and the GUI test rule indeed did trigger.
However… unlike on all the past days since I upgraded to 5.1.0, all my other rules in Rules DSL now triggered, too, without me even touching them. Seriously confusing… 
I will keep an eye on this and run more tests. I will keep you posted if a pattern of some sort emerges.
But, for my understanding. Did I get you right that what is suggested here: No events from Astro binding - #14 by JustinG was never even supposed to work?