Windows Taskbar "lock" problem

Hello, I just want to ask one thing here. Its about this weird taskbar locking problem which sometimes happen. I would like to know what is causing this and how to avoid it.

Here is screenshot:


So, what am I talking about, sometimes this happens, when you cant get from this lock on taskbar. You can use TAB, and lock will move to notification area next to clock. After second press of TAB, it will get to "show desktop", after that to desktop, after that to start orb, and after that, again on taskbar.
My point is, that sometimes, you cant get from this "taskbar lock", and when you are browsing web, and you have browser window in foreground, you can just hover over icons on taskbar, and it "locks" on icons there even if you have browser window active. And when you move away with mouse cursor, that hovering effect will stay there, exactly like on picture... I think, this shouldnt happen.

When this taskbar problem happen, i can just restart explorer.exe and all is back as it should be, but I would like to know whats causing this if you have any idea about that. Maybe some fullscreen apps?

Thank you, I hope you understand.

I dont know how exactly call it, maybe focus? Its just that hover effect (which is shown on Word in the picture) when you put your mouse cursor over any icon on taskbar. It sometimes happen, that this hover effect does not dissappear even if you move your cursor away. Its not so big of a problem, because it isnt happening often, but im just curious about that.
And sorry for my english, but Im not native...