I am using Ubuntu 19.10 and Unity Desktop Environment. Occasionally I can not use my mouse to click on the GUI for any open window. I cannot use the global menu with the mouse or set the cursor in a text field. I cannot click on any buttons.
I noticed for example, if I have YouTube on Firefox in the background, and another application on top, clicking on it makes the video start / stop. It seems to behave as if firefox was the active window but it isn't.

If I kill all applications and reopen the problem persists. I can work around it by log-out my user account and log-in again. I have this problem only after suspending without restart for several days.

is there any place I can look to figure out the cause of this problem?