Problem: Mouse clicks occasionally don’t work.
Symptom: When mouse cursor is over a given widget, it doesn’t become active and click doesn’t work.
In other words, widget becomes unclickable.
Diagnostics: Cursor always moves correct and “xinput --test” reports right position and correct mouse events.
Sometimes clicks work on XFCE panel and inside any application window, sometimes either inside application window or panel.
Sometimes I see another strange behaviour: click acts inside the window that is under the top window.
I’m sure it’s not a hardware problem, because all mouse events are registered by xinput.
Logout and followed session login solves this problem, but not always.
The same problem was in openSUSE 42.2.
Mouse type: A4Tech USB Mouse