Audio problem: Dr. Nora's mother is pounding on the glass of Frasier's booth. She then wags her finger at Nora but the sound of her pounding continues, even though she's no longer doing it.
Continuity mistake: When Dr. Nora's mother comes into Nora's booth, she locks both doors so Frasier can't get in. However, Nora gets upset, quickly gets up and opens the door, without having to unlock it.
Continuity mistake: Near the end of the show, Dr. Nora's mother is chasing Nora through the corridors of KACL, behind the windows of Frasier and Roz's booth. We can see them go by, from window to window. The shot then cuts to Frasier, looking horrified, and we see Nora's mother run by a couple of windows again - even though this could not possibly have happened in real time.
Answer: It equals the record of James Arness of "Gunsmoke" for the actor who's played the same part on TV NOT in a soap opera. If you include soaps there are two main contenders - William Roache, who's been playing Ken Barlow in "Coronation Street" in the UK since 1960. Don Hastings has been playing Robert Hughes in US soap "As the World Turns" since 1960 as well.