He had developed a drinking problem over the years, and the grind of a weekly TV series made it worse. Some of the scenes in which he's apparently just standing, leaning against a wall, are actually shot while he's lying on the floor, which they had to redesign to make look like an upright wall and then shoot from above. He also had a lot of DUIs, ironically, in real life. From Wikipedia:

"Crawford's heavy drinking increased during the filming of Highway Patrol, eventually resulting in several arrests and stops for driving under the influence of alcohol (DUI), which eventually gained him a suspended driving license. While representing the California Highway Patrol as "Chief Mathews", Crawford was known with considerable embarrassment by the CHP as "Old 502" due to his habit of driving under the influence of alcohol ("Code 502" was the CHP police radio code for drunken driving). According to the show's creator, Guy Daniels, "We got all the dialogue in by noon, or else we wouldn't get it done at all. He [Crawford] would bribe people to bring him booze on the set." The show used their CHP technical advisor, Officer Frank Runyon, to keep the actor sober: "I was told to keep that son of a bitch away from a bottle. I think his license was suspended. Some scenes had to be shot on private roads so that Brod could drive." Eventually the drinking strained the show's relationship with the CHP as well as Crawford's relationship with ZIV." [the show's production company]