clicking anywhere in a file make the cursor jump to other open files

Good evening
Running LibreOffice 7.1.8.1 on a Windows 10 machine.
I am really sorry to bother everyone with these (rather numerous) strange problems I am facing.

Also something relatively new (did not happen with earlier versions) - and it seems to happen only with one particular file.

I do have this Writer file open. When I have at the same time any other Writer or Calc file open too,
clicking ***ANYWHERE*** in the said Writer file causes the cursor to jump to the next open LibreOffice file.
I can move around in the file using arrow keys, but using the mouse makes work impossible.
AND .. this happens "when the computer feels like acting up".

Does anybody have any idea what this may be about?

Thank you
Thomas