When you edit the outfit of a (computer-generated) academy youth player his age changes from 16 to 57 after saving. He also retires the next season because of old age.
This bug occurs with youth players born in the year 2000 or later. For some reason, the game seems to change the birthyear of these players when editing their outfits.
Probably the game doesn't reconize the birthyears after 1999, causing the game to reset te birthyear to the first possible birthyear in FIFA 17, which is 1960.
This bug was also present in FIFA 15 and FIFA 16, but only after a few seasons since the first youth players were born in 1998-1999. In FIFA 17, the first youth players are born in 2000 and thus the bug occurs nearly on all youth players.
The bug only occurs on the Playstation 3 and Xbox 360 versions of the game.
To prove my report written above, see the following screenshot which shows a scouted star player with the age of 57 just after changing his boots and untucking his shirt.