LO writer - footnote numbering random restart

After converting my footnotes in a document to endnotes (Tools > Footnotes and Endnotes > Position: End of Document) LibO writer randomly restarts the footnote numbering at some point. I’ve tried right-clicking on the footnote and selecting ‘Continue Previous Numbering’ but with no luck. The problem does not occur when I switch back to footnotes at the end of page. How can I convert my footnotes to endnotes without affecting the automatic numbering? I’m using LibreOffice 5.2.6.2 on Windows 10. The document I’m working on was initially a .docx that I subsequently converted to .odt but the problem persists.