New Mac owner... I attempt to drag a dock icon to a new location on the dock, but it won't let me. The other icons don't separate so the icon will drop to the location I want. Randomly, items will separate when I hover over so I could drop the item between them, but only in that spot and no other locations. What am I missing here? So, I'm unable to put the dock icons exactly where I want them. I've installed all updates.