The Com is "below" the UAM skirt and so makes a light upper stage unstable - the engine fires and the whole stage starts to rotate ...
When I stage away everything but the reentry capsule with the UAM skirt, it looks like it tumbles around an offset CoM which is ~ 20cm below the surface of the UAM skirt (it's a 0.625m model).
The Com is "below" the UAM skirt and so makes a light upper stage unstable - the engine fires and the whole stage starts to rotate ...
When I stage away everything but the reentry capsule with the UAM skirt, it looks like it tumbles around an offset CoM which is ~ 20cm below the surface of the UAM skirt (it's a 0.625m model).