Hey Marc and Peter,
Although I have not noticed a problem with BIAB in particular, there does seem to be something a little "funky" with Yosemite's handling of "front window" focus (at least on my machine).
I'm not sure if this is related or not, but here is what I have experienced since upgrading to Yosemite…

Very intermittently (once a week or so), I have noticed problems with input from the keyboard not being recognized in certain applications (It's happened to me in TextEdit and Mail among others).
I will be typing away and notice that my text is not being entered, even though the window is highlighted, and the application menubar is the frontmost application.

I have to click on the window again, and even though there is no visual change in appearance to the window highlight , that window once again accepts the keyboard input.

This not only happens with application windows for me, but also on the Yosemite login screen itself.
Normally when the OS X login screen appears, I can type the first letter of my account name "J" and the icon for my account will be highlighted, then I can keep typing to enter to my password.
However about once in 10 or 12 reboots, I can type all I want and nothing is recognized, until I click on the background of the login screen, then the keyboard input is recognized.

I was in on the Yosemite beta test program, and did file a bug report about the intermittent loss of focus on the login screen.
I got a response from Apple, that someone had already reported this bug and it was being investigated, but it's still happening here intermittently in 10.0.2 over a year and a half later.
I have tried a clean install of Yosemite and this still persists.

As I said it seems to be HIGHLY intermittent (on my system at least), so it's been really hard to nail down and since it's not a major pain in the butt to click once more, I've been living with it.

Marc, you described it exactly!
It's as if some background process steals the focus momentarily, and then is unable to cleanly restore focus to the frontmost application window when it goes back into the background.

Sorry for such a longwinded response, but your problem seems like it might be related to what I've been experiencing, even though I haven't had it happen here with BIAB yet.

I'd be curious to hear if other folks have noticed anything similar since upgrading to Yosemite.


- Jay

MacPro 5,1/12 core@3.46GHz -- OS X 10.15.7 -- ATI 7970 -- 32 Gig RAM -- Crucial 500GB OS SSD -- Samsung EVO 1TB Audio/Sample SSD -- BIAB 2024 -- Logic Pro X -- Cubase Elements 14 -- Too many plugins