Thanks for reporting the problem. It sounds like it is the new bug that was introduced when the PHP PCRE script was updated to version 8.21. I contacted my host to see if they can downgrade it to version 8.20 which is supposed to fix the problem but haven't heard back yet.
A work-around is to simply copy/paste your old post into the edit box and then save the edit. That should work.
Thanks for all your interesting contributions to our discussions.