I have two issues with dock. I'll start the thing that happens too often.
Dock is hidden behind windows. I have dock set to be auto-hiding so that it only shows up when my mouse is bumping the bottom of the screen. But way too often the dock is hidden behind the windows I have open. Of course I dont want it to open up if I have a game or something like that in full screen mode, but this happens for everything.
Second issue is more rare. rarely when I bump my mouse at the bottom of my screen to get the dock to unhide and I move my mouse up towards the apps I want to click on, it just hides again as if the mouse isn't on top of the dock.