Please refer to this URL on the Ask LibreOffice site for details. https://ask.libreoffice.org/en/question/70623/libre-office-4282writer-bug-with-outlining-mode-is-there-a-workaround/#post-id-70632
Affects LibreOffice on Linux and LibreOffice Vanilla on OSX. (other OS's could be affected)
Thanks for the bug report. It looks like this is a duplicate of bug 83103. I can see that it triggers starting from one character shorter numerals than the other one, but the cause must be fundamentally the same. *** This bug has been marked as a duplicate of bug 83103 ***
*** This bug has been marked as a duplicate of bug 56258 ***