I just upgraded to LibreOffice 5.0.3.2.
I saved a file to docx format and sent it to my colleagues, who could not open it. Sure enough, when I opened it myself using Word, I got an error saying “The Open XML file filename.docx cannot be opened because there are problems with the contents or the file name might contain invalid characters” The file name did not contain invalid characters. I moved the file to another computer where I had not yet updated LibreOffice from 5.0.2.2, and was able to save as docx without a problem. Is the docx conversion in 5.0.3.2 broken?