Yosemite Mission Control Spaces Problem when restarting (Retina Macbook Pro 2012)

I don't have an answer but this happens to myself as well; You are not alone. Rather frustrating bug. No matter which options I check or un-check in System Preferences every restart each space from my 2nd monitor and my HDTV appear as a space on my main display. This is also messing up my assigned Desktop pictures.

I'm having this too. Spaces from my 2nd monitor keep transferring to my 1st and wallpapers keep resetting.

Seems to be a bug that's occurring when the main desktop is set to a display other than the primary hardware one.

If you go into System Preferences - Displays, under the Arrangement tab, drag the menu bar over to the other display, then arrange your spaces/wallpapers as you want them, your setup should stick after reboot.

Not an ideal solution, I know, but maybe it'll do until Apple fixes the bug.

Thanks Carl, your trick worked. I hope Apple addresses this issue with 10.10.1 update, which is probably a week or so away given Apple's usual 10.X.1 updates.

Exactly the same problem I'm facing...

Here's another possible fix:

Try resetting the SMC and PRAM as detailed by Luis_Mercado in this post: Guide: How to solve Yosemite memory leaks and CPU usage

Some users reported it completely fixed this issue (among others) for them. So it's worth giving it a shot.

It fixed my main display for me, but my second monitor still resets for some reason. But at least I can now arrange my desktop as before and have the setup stick on my main display. YMMV

It is already update 10.10.1 and the issue persist.

Besides of reseting spaces and putting them all together in one screen, I have seen that while I work, the system re-positions the full-screen spaces on its own; they change positions during my session..... weird.

My second monitor spaces would populate the 1st monitor spaces ad nauseum after every restart/shutdown using 10.10.3. All my spaces have their own distinct desktop picture - which is the way I like it. Once the system restarted I'd drag all of the 2nd monitor spaces back over to the 2nd monitor and I'd continue on until the next reboot...

What I started noticing however was that the one background of the only space left on the 2nd monitor after a restart, was actually the same desktop picture of the 1st space on the 1st monitor. I'd gotten into the habit of eliminating that particular space immediately after I'd finished dragging the others over. Being more lazy than normal one day, I decided to leave that rogue space alone on the 2nd monitor and not to delete it. So I had two spaces with the same background... I could live with that until I wanted to eliminate it again... lol

ANYWAY, it seems that having left that rogue space in place actually solved this irritating problem with Yosemite spaces for me.... any subsequent restarts populate the correct spaces on the correct monitor!

2012 Mini i7 2.3, 16gb memory

I forgot to mention - this only works for me with a soft reboot... a hard reboot and I'm back to repositioning the screens back to the 2nd monitor.

Add me to the group, same problem here on both my MAcBook Pro and Mac Pro after each reboot, strangely on the Mac Pro the problem also occurs every time the machine wakes up from sleep...still not fixed in 10.10.4.....

Have you tried Mission Control Preferences/Displays have separate spaces?

indeed, I am aware of this option for a long time (spaces had lots of problems with multiple display set-up when mountain lion or maverick was released, don't remember which one it was) and having it on or off does not make any difference on the MacBook or Mac Pro.