It`s normal situation. When GK reaches CA 5 and when player reaches CA 7, they don`t get improvement from training anymore. They only get improvement from playing games, and reach their LA.
To be precise, when GK reach CA5.9, normally 453,333G without counting experience
plus, daily training will not improve him any more. Through the bonus from VH training still exist.
For an outfield player, the limit is CA7.1, 586,666G without counting values by experience