Some aspects are just too complex to simulate. The fluid dynamics of nearly supersonic flows of cryogenic liquids that suddenly turn into white hot gas is… intractable.

The failures Starship had were often to do with simpler engineering bugs that they’ve been ironing out, such as: leaks in piping caused by violent shaking, explosive gases accumulating in closed spaces, filters getting clogged by ice forming in the cryogenic tanks, and burn-through of an experimental heat shield design at moving joints.