IIRC, the exhaust nozzle on the B rotates down. Only watched the video once but kinda seems like touchdown in a pretty much normal VTOL attitude but then the tail rises and the nose dips.
Exhaust nozzle malfunction in the transition from VTOL to level flight? IE: VTOL/nozzle down and touchdown. Transition to level flight for taxi in (nozzle rotates to level) but nozzle remains down. Pilot adds power, tail rises kind of deal?
Who knows at this point. Who knows if they will ever release what really happened.