Can you clarify this? selectedDisplayChanged_ modifies:
this.maxModeIndex_, this.selectedModeIndex_, and this.immediateSelectedModeIndex_

I don't see any observers tied to those values?

I don't recall exactly what the race condition was. It occurred when the selectedDisplay was changed, but the observer was triggered later on as opposed to immediately. This led to some values that had to be updated in the observer not to be updated in time for usage and thus their older values were used.

I'll leave this open if you want to continue to investigate, but without more details or a symptom, I'm still a bit fuzzy on what/where the problem is. I'm lowering this to a P3 to reflect that without more details this won't block the MD Settings release.