Can’t reproduce this but reporting in case it happens again or to anyone else.
I had an item synced to GCal. In GCal, it appeared at the right time but the event name was “(no title)”. When I then opened Legend, I saw the event with proper item text on a calendar view for a brief moment and then the item text disappeared. The item in the outline just had the date/time with no text. So it acted as if the text was erased in GCal and that synced back to the item in Legend, but I definitely had not touched the event in GCal.