Always thought that “Southern technical difficulties” bit was a joke.
On “Laugh-In” in 1968, James Garner said to the lovely (and black) Chelsea Brown, “Your place or mine?” She smiled, the two linked arms & they strolled off stage.
Wolfgang the German soldier: “Verrry interesting. But right now in Birmingham dey are showing a test pattern!”
It did happen on some occasions particularly in the 1950’s and early 60’s and especially in Jackson,MS at Channel 3.
Liberal groups went to the FCC on fairness grounds to change ownership of the station in the mid 1960’s.