Bug in composition mode for multiple screens?


Looked around for an answer about this, but couldn’t find one, so here goes:

I’m running OS X 10.11.4 and Scrivener 2.7 (26106) on an iMac. When I enter composition mode, all screens (I’m using three) briefly go black, and then the main screen shows the document. However, instead of the other two screens remaining black, they return to normal. I can see all their windows, and interact with them. I have “Blank out other screens” checked in preferences, so I expected that the other two screens would remain black.

Is anyone else seeing this, or is this a known bug?