Why are clan challenge games allowed to continue when a player is no longer a member of a clan? If a player leaves a clan while playing clan games, why aren't those games either declared draws or awarded to the other player? Playing a clan game against someone who is not a member of the challenging clan doesn't make sense to me. Is there a way to fix this anomaly?

no. it's fine the way it is.

Yeah, I'm with trev here. Clans shouldn't be penalized because one of their members wants the fourth clan space; also, plenty of people legitimately drop their subscription but want to complete their games for clans that they still feel like a part of.