Jessica Savitch showed up for a newscast obviously impaired. She claimed it was a prescription drug reaction, but I think it caused her to lose her position. She was big star at the time.
"There are numerous stories of her bizarre behavior on and off the set; screaming rants, cocaine binges, promiscuous weekends--all the usual trappings of a celebrity on the skids. By 1983 Connie Chung had replaced her on the Saturday edition of NBC Nightly News, and "Frontline" had nearly eliminated her on-screen appearances. Three weeks before her death she delivered a mysteriously slurred and bizarre "NBC News Digest" newsbreak, and was nationally humiliated. It would be the biggest, and last disaster of her professional life."
I believe it was her cocaine addiction.