Yes, it still happens, and it does matter, because the inactive split is always obscured by the active one, the bug means that when coming out of full screen, the reverse is true.
At startup, both splits are in "Audio". Audio consists of 3 panes, the first of which is a custom, expression based field (as opposed to an expression based pane)
if(isequal([album artist (auto)],/(multiple,8),/(various/),if(isequal(mid([album artist (auto)],0,3),the,1),mid([album artist (auto)],4,1),if(isequal(Mid([album artist (auto)],0,1),1,6),0 - 9,Mid([album artist (auto)],0,1)))followed by [album artist (auto)], then [album]
The expression field is called 'Artists' and MC launches with both splits loaded at the [Artists] level of the library browser.
At launch, MC always designates the same split as the 'active' one, and that is the one I see, the other is minimised right down at the bottom out of sight.
I switch to "Images", which is a panes view with thumbnail list, and double click the first image. This displays full screen on the monitor.
I double click again, and standard view returns, but the visible split is now inactive and tree selection is "Audio" as per the now active, but hidden, split.
That's the bug in a nutshell, and it makes no difference if I choose videos instead of images. It makes no difference if I double click, use ctrl+3, ESC, ctrl+1, click the close display button etc. etc.
Now, because you say you could'nt produce it, I poked around some more, wondering if library views had anything to do with it...
If I bring up the 2nd split (audio) and change it to panes view, then go back to split No.1, full screen and back again does not de-activate the split ?
If I then browse to a different image viewscheme, and double click an image, then double click again, the bug is back and the split is once more, inactive.
If I then go back to the 2nd split and change it back to a library browser view, then go back to split 1, everything works again.
(sorry, you still with me?
)
Other things cause it to trigger too, most reliably found so far is to go to an existing smartlist and use the wizard to add a playlist exclusion to it. After clicking OK in the wizard, MC switches the active view at the same time as it refreshes the smartlist.