Burning propellant ejected
The model was perhaps 15 feet in the air when the propellant (and delay grain/ejection charge) all went out the front in literal balls of fire. AltimeterThree aboard reported an apogee of 48 feet. Baffle blown out, motor was ejected and was on the ground next to the pad with the nozzle end packed with dirt. It hit the ground with quite a bit of force.