start /wait soffice --headless --convert-to pdf:writer_pdf_Export FILENAME.rtf
works fine when LibreOffice is not running, but fails without warning if LibreOffice is already open on the desktop.
Same problem on linux. Changing the platform to All.
*** Bug 38519 has been marked as a duplicate of this bug. ***
*** This bug has been marked as a duplicate of bug 37531 ***