I dont know if it happened to anyone else, but it happened to me twice today. It is a bit complicated to explain, I'll just try.
Person A: Sand Clan
Person B: Uchiha Clan (most likely any clan)
Person A uses tsunami and catches Person B. Person A dies during tsunami (because of inferno or smth like that). Now when tsunami is gone after a while, Person B can't use any jutsu. Relogging fixes the problem, but thats annoying as fuck when you raid and you have to melee fight as Uchiha.