miconda left a comment (kamailio/kamailio#4275)
Well, if I understood correctly, the code replaces the unique ETags of the presentity records with a predefined value (ie., `#-OFFLINE-#'`) in order to delete the records later, but that can lead to infringement of unique constraints. So the current behaviour seems to be an uninspired `solution` based on this report, so we have to look for alternatives that are compatible with the internal DB API, without relying on raw queries.