https://www.metv.com/stories/how-buddy-ebsen-learned-to-relax-on-the-set-of-barnaby-jones

It took a talk from Ebsen's wife to get the actor to calm down.

Its apparent he started to relax because the last few seasons had Betty and JR take over investigations. I always loved Betty focused episodes although I may be in the minority. Doing a hour series is lots of work compared to a 30 min sitcom. Lee Majors was on 2 hour long series and it broke him. He said that he had to be in almost every scene which requires so much work.
Buddy transferred to a silly character on the Beverely Hillbillies to a former cop private detective very well. When he spoke, his word was law. Barnaby seemed to always be right which made a fantastic detective.