Left mouse button randomly stops working

I am struggling with my left mouse button. It stops working at random intervals -- sometimes after 5 minutes, other times everything is fine for 5 hours.

It's NOT a hardware issue. I have tested an external USB-mouse too, and the same issue occurred.

I can temporarily solve the problem by jumping to the text-only console (Ctrl+Alt+F1) and going back to graphical desktop. However, after some minutes or hours, the same problem returns.

I have tried different desktops and users too (Gnome, Mate and XFCE). In every desktop-environment, the same issue occurs.

The left button issue is different from time to time. Sometimes it's like my left mouse button is clicked permanently, sometimes it doesn't react to whatever I do. The right mouse button and cursor movement are never effected.

I have already tried to solve my problem using Google and StackExchange guidance (i.e. this), but the advice only ever delivers temporary fixes.

I am looking for a permanent solution.

Post where I am logging tries and possible solutions

I have exactly the same problem on a Sony Vaio with Xubuntu 16.04, but the left mouse button stops working about every third hour, both on the touchpad and on the external mouse. To date I have been logging out and in again to fix it. Recently I found this alternative.

sudo modprobe -r psmouse
sudo modprobe psmouse proto=imps

Works fine for the external mouse, but the touchpad gets slow and stops scrolling. However, after entering the commands the hanging never bothers me, not even after a full workday.