Shanters jerkiness is no secret. He does seem to have mellowed with age and having quit drinking. It's incredible he keeps going and flew into space at his age. The irony is Bezos's own jerkiness overshadowed Shanters when you watch the video after he landed and Bezos is spraying campaign around a recovered alcoholic. Maybe Shanter lived so long in order to redeem himself? That'd be a very Kirk thing to have happen.