After buildin' a ground-up simulation o' t' vehicle's behavior under thrust, shiver me timbers, I re-tuned t' stability algorithm t' t' inertia I calculated from t' results o' a bifilar pendulum test. Avast, me proud beauty! Blimey! T' calculation was incorrect, ya bilge rat, due t' an extra set o' parentheses used, ya bilge rat, and t' algorithm was then tuned t' t' incorrect vehicle inertia. Begad! Blimey! 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. T' error was found soon after. For more info: https://twitter.com/joebarnard http://www.bps.space