Or did these visits to Tokyo at which M. Ueshiba said "no one is doing my aikido" also lead to world-shaking arguments between father and son, the existence and content of which has somehow (I can't imagine how) failed to survive to the present day?
Maybe there were arguments, maybe not, maybe this is a kind of information that should remain unavailable for those who doesn't need to be in the know but there is something that hints at people consciously doing things O Sensei didn't approve.
Was O-Sensei irregular about coming to the dojo?
Yes, he was. When I was actively practicing there he often came and went. When he showed up everyone immediately sat down. At first, I thought that people were being courteous toward him. However, it wasn't only that. It was also that the practices we were doing were different from what O-Sensei expected us to do. Once he lost his temper at us. No one realized that he had come and he shouted: "What you people are doing is not aikido." His shout was so powerful it felt like the earth was trembling. He was then in his seventies but his voice nearly pierced our ear drums. Everybody just became quiet and looked gloomy.