write error message when I try to save odt document

Since I upgraded to Mac High Sierra, I am unable to save odt documents (can save docx files.) I have upgraded to 5.4.6 but that made no difference, then tried 6.0.3.2, with no difference. I use an older version on my laptop in Sierra with no problem. Error message comes up:
C:\fakepath\Screen Shot 2018-04-06 at 5.50.57 PM.png

I also find LibreOffice unstable, crashing easily, and going through rapid-fire attempts to save documents.

(Edit: activated image -AK)