I was there today, too, and was really scared that Gringotts wasn't going to open at all! It was listed as "closed" on the app throughout the morning. Eventually we made our way there (around 1:30 pm) and rode it with a 150 minute wait. The wait was brutal. We didn't realize it would mostly be outdoors... soooo hot. When we were on the stairs about to board, there was an announcement that the ride had broken down. The CM looked pained as she explained she would get us more info when she could. The ride was quickly fixed and we got on! We LOVED it. Gringotts was such a great ride.
We were in Diagon Alley around 3 and saw a stretcher being brought to Gringotts. I assume this had something to do with the ride going down.