Reporting strange behaviour.
I generally use all the apps in full screen mode except when copying between them. Upon exiting full screen, the libreoffice window disappeared. It could still be found in the taskbar but on selecting it, you couldn’t see it. Once, on about the 5th try, it showed up as a 1cm (1/2’) square but it did not respond to stretching or ctrl+shift+J or F11. It never appeared again. I copied the file itself into a new file. That tiny window responded to stretching. Yah!
Weird though, when I deleted the original file and renamed the new one, it again disappeared just because of the name… “20300000 Case links.odt” Nothing special in the name. Renamed to include the (copy) and it works.
I am working on a new LMDE linux system.