Error with my Fantasy League, please help

Last night i removed my flex position player Jesiz from my League, I tried to add Gamsu to be my new Flex player. It told me "The exchange would leave your team with an invalid starting roster, with too many players in one position." He would be my second top laner since he it's a flex role. Shortly after I tried to just add Jesiz back to flex and it won't let me add any player to my flex role. (So not too many toplaners) These are NA players so they aren't locked yet, but it looks like i'm going to be down a player anyway. Can anyone help?