I hadn't heard that but I did read an interview where Griffith admitted that he was starting to show up late for work and not know his lines. He outright said it was very unprofessional. But he felt the show had degenerated into being just another comedy show. Don Knotts was gone. Ron Howard was old enough that Opie plots tended to revolve around Opie and his friends or Opie on a date rather than the father- son relationship. He felt the qualities that had made it something special were mostly gone.