I’ve only been on TV a couple of times and don’t think I’ve made any major cock-ups there. But I have left the mike on during a radio show and used foul language with the sound technician. It was quite embarrassing, and everyone was listening.
I also made the major error of mixing up the radio station names at a different station and, even though I’d been working there for months, I accidentally said the name of another station one day (one I’d worked at years earlier, don’t know why). They did not fire me, but they should have. I felt really bad.
I’ve made several other mistakes too, of course, including getting names wrong and so on, but nothing that major or embarrassing.