Excerpt from a integration of the full spin Hamiltonian ℋ for 10⁵ orbits, using the (triaxial) moments of inertia of Hyperion but orbital eccentricity e = 0.01. The region highlighted in green shows the barrel instability (Ćuk et al. 2021), characterized by irregular spin rate (bottom row), obliquity (fourth row), and roll on the long axis (top row, light blue) but a clear preferred orientation of the long axis towards the primary (third row). Analysis in Andoyer coordinates and in the framework of nutation-orbit resonances shows that this behavior is associated with libration of the 2𝑔 + 2λ − 2M resonant angle (second row).