After upgrading to Mavericks, Dock randomly moves to secondary screen

Question

I've seen a few quirky things since upgrading to Mavericks, (backup taking forever, updates I know to be available not showing, etc.) but this is the strangest.
I have a MacBook Pro mid 2012, 15", non-retina with an externally connected (Thunderbolt to DVI) Dell monitor. I have the displays set up such that the MBP is the secondary monitor, and the Dell is the primary.
Randomly (I know. Nothing is random.) the Dock will just move over to the other monitor (MBP). A couple of things to note.
Looking in Display Preferences, the dell monitor shows as the primary (ironically still indicated by the presence of the menu bar, despite the fact that the menu bar is now on both screens post-Mavericks update), even though it doesn't have the dock.
Switching the primary (by dragging the menu-bar-thing in Display Preferences) to the MBP and then back to the Dell monitor moves the dock back to the external display.
Outside of System Preferences, clicking the Apple in the menu bar and going to "Dock" >> "Dock Preferences..." If I change "Poisition on screen" from Bottom to Left and back to Bottom (without closing the preference sheet) switches the dock back to the primary monitor.
Anyone else seen this issue?

Answer 1

It is a very, very UNUSUAL GESTURE.
You have to PULL DOWN and do that to a point BELOW THE BOTTOM of the Mac screen.
If you merely point the mouse at the extreme bottom, that WILL NOT do the job.
If you point the mouse at the  bottom. And then say, oh wait I have to pull down "further"... that will not do it!
You have to begin say 1cm above the bottom, and pull continuously (without stopping) to a point BELOW the bottom.
I've never seen that before in a Mac (desktop) gesture.  It's very "iOS".  Bizarre stuff!