I also understand that some.. er.. disagreement over Ambha Love possibly singing this contributed to the ending of the C50.
I don't think that caused anything to do with the 50th reunion ending. It was more a symptom of things than a cause.
I don't believe the reasons Mike gave. I think Mike didn't like the amount of adulation Brian was getting on stage. At the penultimate show Mike described it as 'a show in two halves - first half and second half'. Of course it was a show in in two halves in more ways than just that. Maybe Ambha wanting to do SOS was one of the flashpoints. Maybe there were other flashpoints too.
From what I remember, there was no problem with her singing SOS. Back then the anecdote was that Mike asked Brian if Ambha could sing SOS and Brian replied
jokingly "But I was gonna sing it!" but had no problem with it. Of course even back then people already said that Mike wanted to push his daughter in the spotlight etc. but that was not what the report I heard suggested.