Dock bar changes settings and monitor on its own

[MR_Boogy]

I've an iMac Retina 5k with an external monitor. The built-in 5k display is my primary where the dock lives at the bottom.

I noticed the other day that my dock bar had started auto-hiding, despite me not changing this setting.
Jus now, I noticed it had jumped to the bottom of my secondary display. I couldn't find a setting how to control this but setting it from bottom -> left put it on the left of the 5k monitor, then left->bottom it was back in the right place.

 

[chabig]

With multiple screens, the dock follows your pointer. Whichever screen has the active pointer displays the dock, which makes sense because that's the screen you're working with. Also, the dock hides automatically regardless of the setting in System Preferences.

 

[OldEightBall]

I beg to differ. I haven't experienced the unwanted/un-asked-for autohide, but the hopping dock has been happening to me on occasion since Catalina. It seems to happen when the mouse makes a very rapid move from the built-in 5K to the external 4K near the bottom of the screens.

 

[MR_Boogy]

I was just testing and it seems @chabig is partly right. If I swipe the cursor down to the bottom of my 2nd monitor, the dock pops up there... and then remains there, unless I do the same on the Retina and it returns there.
I guess this is what I did without realising.

The dock doesn't simply follow the cursor though, and the dock definitely doesn't autohide at all times. I have to explicitly pull the cursor down to get this functionality.

 

[OldEightBall]

I see the same behavior. I can't "swipe" as I have a mouse vice a trackpad, but pushing the cursor all of the way down and holding there for a moment triggers the hop for me 4 out of 5 times (must be a timing thing for that one out of 5). Thank you OP for this. Now I know that I'm just a little "mouse happy" and not having a problem.

 

[chabig]

I was just testing and it seems @chabig is partly right. If I swipe the cursor down to the bottom of my 2nd monitor, the dock pops up there... and then remains there, unless I do the same on the Retina and it returns there.
I guess this is what I did without realising.

The dock doesn't simply follow the cursor though, and the dock definitely doesn't autohide at all times. I have to explicitly pull the cursor down to get this functionality.

I think you described it better than me. My behavior is the same as yours. When I move the pointer to another screen, the dock doesn't appear until I move the pointer to the dock area. Once it appears, it stays or hides according to the auto-hide setting. The same is true when moving back to the other display.

I believe this was new in Big Sur and it carries over to Monterey.