Field of Fear, ‘Trade not available’ message

Field of Fear’s iconic Bruce Matthew’s will NOT accept exchange of epic FOF’s Bruce  Matthew nor Micah Parsons. I have already earned the first of two iconic Bruce Matthew’s, both needed to obtain (along with two more epic Bruce Matthews) a mythic Bruce Matthews. The mobile game is not allowing me to obtain the second iconic player. Am I doing something wrong here? The Epic FOF players are both accepted as exchanges elsewhere. Am I alone with this problem? Thanks!