After buildin' a ground-up simulation o' t' vehicle's behavior under thrust, I re-tuned t' stability algorithm t' t' inertia I calculated from t' results o' a bifilar pendulum test. T' calculation was incorrect, ya bilge rat, due t' an extra set o' parentheses used, and t' algorithm was then tuned t' t' incorrect vehicle inertia. Begad! T' calculated inertia was much smaller than it should have been, so t' simulation predicted a vehicle requirin' less control authority, hence t' loose oscillation durin' t' test. Begad! T' error was found soon after. For more info: https://twitter.com/joebarnard http://www.bps.space