I'd speculate one of main tank bulkheads breached and gas kept leaking from payload door which overpowered RCS. Then, during reentry, the vehicle briefly manage

I'd speculate one of main tank bulkheads breached and gas kept leaking from payload door which overpowered RCS. Then, during reentry, the vehicle briefly managed to regain attitude by aerodynamic forces on the flaps, but became north-northwest aligned and broke up.