When you go and chec characters under some show, lie, for example this...
https://www.tvmaze.com/shows/909/perry-mason/characters
...you can see that main cast is listed twice. Both under "Main Characters" and under "Recurring Guest Characters". I've been noticing these things since I joined the site and I always found it weird, but only now do I realise that this is a bug of some sort. There is no reason why main characters should be listed one more time with all the rest under under recurring guest characters.
Okay, I see the problem... main characters are incorrectly marked as "guest" in one episodes which makes them appear under both main and guest characters. But shouldn't there at least be a different number of appearances in such cases?
If a character was main in say first 3 season and total of 66 episodes, but then appears in season 8 as guest character, s/he shouldn't be added under both main and guest characters with 67 appearances, but 66 as main and 1 as guest, no?