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What gives? Examination of the case contents the next day showed that the delay grain had leaked big time. The O-rings were all eaten away on one side, and the CPVC tube the delay was in was throughly blackened on the other side.
From the appearance of the movie, the parachute must have ejected immediately upon launch, and the rocket is dancing with the open parachute.
Note the thin trail of smoke to the left of the lower spark-arc, and continuing to the right of the upper arc. I suspect this is the front end of the airframe, now open, and ejecting some of the motor gasses. The forward end of the airframe was hot upon retrieval, and contained some burned-propellant-like residue.
How did it happen? I am guessing that the delay grain was not seated perfectly, allowing an O-ring to slip into the head end recess and create a gap.