Results:
Some likely issues were that the stability was too high because of how big the fins were, which also caused the rocket to turn into the wind, so the rocket spun around a lot and was messed up even by the relatively calm winds, the motor's ejection charge delay was too also too low, and the altimeter was mounted right up against the foam protecting the egg without any holes cut out for airflow, so it may not have gotten a very accurate reading.
OpenRocket simulation file used: SqHS openrocket 1.ork