Did Arthur and Bryan conflict anywhere was effected by their bi polar states. I have read somewhere from an interview that Bryan was bi polar as according to an interview his mom gave in '08 or '09. And people here can agree with me that Arthur might've been too. It might've been a factor, drugs too, and maybe "Stephanie Knows.." bs
Creative differences likely played the biggest part.
When the bi-polar kicked in is unclear--I've never read that Bryan was unusually erratic at the time (as Arthur or Gene Clark could be even early on)--by all accounts Bryan was just a funny fun guy & prankster though a pain in the butt sometimes (who isn't?))...could have been after Love, but drugs and alcohol were the self-medication of choice in those days when it was not always treated as such by the medical community. ..they were just alcoholics or druggies, especially if you were one of those "long-haired hippie freaks"
And not to make light of a very serious disorder...it seems that the designer (drug company) disorder of the day is Bi-polar or autism.