Can't change adult positin

I am trying to change the position of an adult from a Tiger Cub Adult to the Cub Master, but it says “ERROR position cannot be updated”.

What going on? How can I fix this?

Tiger Cub Adult isn’t a registered position. Someone would end up both a Tiger Cub Adult and Cubmaster because their tiger still needs an adult partner. Best guess is to have them do an application rather than a position change.

Use add existing member so that they show up twice.