Which part of the trigger doesn't work? All of it or just the Private Boolean part? How are you determining the state of Private Boolean for the first triggered rule (to know that it is not working)? Were you expecting the first triggered rule to run when the second trigger runs? It will only run when Master Bathroom Motion Sensor goes active.
I duplicated as best I could, and it works. However, for Rule 1, I see the Boolean is showing as [FALSE] yet in the Rule Status screen, it's showing as true AND the lights I have config'd to mimic yours all do something.
[FALSE] in the screen cap above but true in the one below.
I have two Motion sensors here in my office: MultiSensor6J mimics your "Master Bathroom Motion" while my Office Wallswitch mimics your "Justin Bathroom Light"
My Rules #2 & #3 uses my 2nd Motion Sensor to mimic what I believe you do with a "shower" motion.
So.. it all begins with the "bathroom" light on, because Rules are initialized with boolean = true.
I then move to trigger only the "shower" motion, and the other light comes on, and the "bathroom" light goes off. I sit still and the "shower" motion ends and the lights reverse: other goes off, "bathroom" goes on. BUT, like you, Rule #1 shows [FALSE]
I can confirm there is a bug with this. I'm able to reproduce something similar, where the Private Boolean has been set to true by another trigger, but shows as false. Will have to dig a bit to see what's causing this.
Found the bug! Not sure how it went unnoticed before, but I can tell you that a comment in the code suggests it was working and then broken (something essential was removed by a comment). Fix will be in the next release.