I am seeing the message (screenshot attached) saying “One event on invalid date at…” after I set the “once” dates. The format changes from “mm/dd/yyyy” to “yyyy-mm-dd”. The event shows up on the correct date, but the default “Recurrence Description” uses that phrase “One event on invalid date at 5:00pm” (or whatever the time of the event is).
This appears to only be a problem if I don’t insert a custom “Recurrence Description”. It occurs to me it may be associated with the sort order bug going on when you click “(see all)”. Just a speculation.