[Phssthpok]

Recently, while editing several different books on Windows 10, I've hit "save" and been greeted by an error message tell me that META-INF/container.xml in the temp directory (somewhere in AppData/Local) is not found, and the file is then basically toast. Sometimes it's just the container.xml that's vanished, which I can manually recover (but it involves unzipping what's left of the epub and adding it manually, which is an annoying and long-winded process) but sometimes all the images are gone as well. Presumably there's something that's cleaning the temp directory that wasn't there a few Windows updates ago, or anti-virus updates or something. (Anyone know what it could be?)

Is there a fix for this that anyone can suggest, e.g. specifying a different temp directory? And if I do something like that, will the temp files be deleted when I close the editor or would I have to clean them manually?