gcanyon parent
That makes it look pretty clearly like one of the fuel vessels overpressured and ruptured.
Scott Manley observes the breach was in the cargo section, and not at the PEZ dispenser door. It appeared to split longitudinally. There are header tank downcomer lines that might fit that bill.
The part that I found interesting was ~"Anyone can build a bridge, but it takes an engineer to just barely build a bridge. That's what Starship V2 is, a mass and complexity reduction. Maybe they took away too much."