This is a simple issue, but it's kind of hard to explain, so please bear with me.
Has anyone else had an issue with panel buttons sometimes being "unclickable" if your mouse arrow is on the outermost edge of the screen? - Almost like there's a row of pixels surrounding the actual button.
In other words, consider how the "show desktop" button is normally in the bottom left corner of the screen. This is convenient because you can quickly and blindly move the mouse to the bottom left corner and just click, and everything will be hidden. One can imagine cases where this is useful...
Well, the issue I've been experiencing on 18.04 is that if I do that, it doesn't always work, but on 16.04, it works every time. I found that sometimes I need to move the mouse a little and keep attempting to click until it finally "accepts" it.
I'm running the traditional theme, and the same issue occurs with the "Applications|Places|System" buttons when the mouse arrow is on the very top of the screen.
Should I report this as a bug somewhere?