Following up from my last post, I am getting unexpected behaviour when going fullscreen on multiple displays. Seems like a bug to me.
In the attached I have my screens layout, namely one laptop and two external displays. There is a minimal composition (archive.zip) that illustrates the problem. There are photographs of the result, one before the periodic event for fullscreen, and one afterwards.
In essence, the two windows position themselves on the correct display but on fullscreen they both go fullscreen on the same display (in the photos the red window is behind the blue one).
Still playing ... any suggestions, if only for a work around.