Yes, same thing happens to me. I have a 3 monitor setup.
The order they are in is 3-1-2
I can move the dock to and around the Primary Monitor no problems. (I have this dock on the side of the screen)
I select >Monitor 2 and it moves there and I can position it around. Again no problems
But...When I go back to >change monitor it shows up with Monitor 3 checked off (when I had selected monitor 2).
I reset the position back to >Primary monitor (works fine) then I select >Monitor 3 and it moves the dock back to Monitor 2.
I find this strange because I did have the dock on monitor 3 for a while at the start of the beta, but it kept randomly moving the dock back to the Primary monitor and close to the middle of the screen. Not attached to the side where I wanted it.
