For anyone getting this bug, I've found a workaround.
I'm using the Playoff Roster. You need to download REDitor, open up the roster, go to ID lines 1068 through 1113. All the PlTypes should say 1. You need to change all those to 3.
For some reason, when you created a player it would make multiples of the same player and change everyone's nicknames to the name of you player. With these changes, it should work.
I've tested this in MyPlayer and with CAP and it seems to work.
EDIT:
Forgot to add, thanks slimm44 for the great work. Really liking everything so far!
EDIT2:
Seems like there is still a problem with MyPlayer. I can make a player with no duplicate names but it doesn't track your stats. So every game will be your player's "first" game.