= Solution
For three distinct positive <principal moments of inertia>, the denominator of $p^2$ is positive. If $I_3$ is the largest moment, the two numerator factors have opposite signs, so $p^2<0$. If it is the smallest, they again have opposite signs. If $I_3$ is intermediate, the two factors have the same sign, so $p^2>0$. Thus the <intermediate axis theorem> gives
$$
\boxed{\text{largest or smallest principal moment: stable;\qquad
intermediate principal moment: unstable}.}
$$
For the stable cases the body-frame wobble frequency is
$$
\nu=|\Omega|\sqrt{\frac{|(I_3-I_1)(I_3-I_2)|}{I_1I_2}}.
$$
The perturbation does not decay in the torque-free conservative model. For the intermediate moment, a generic small impulse excites the growing branch and eventually leaves the linear regime.
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