The above is a screenshot showing the top left region of my monitor. There is a Notepad++ file open with five lines of meaninglass text. I have just selected part of the text (grey), have right clicked and I am about to click on 'copy' to copy that text to the clipboard.

The image below is what appears immediately afer I have clicked on 'copy':  The Notepad++ window has shrunk to just three buttons in the top left corner of the screen.  I cannot continue with Notepad++ until I have clicked and dragged on the edge of that small window to make it a useful size.  The text has been copied to the clipboard as intended.  I have now discovered that the same thing happens with 'cut' and 'paste' as well as 'copy'