I think that the problem is in the way names for "regens" (youth players, scouts and such) are handled:
http://soccergaming.com/index.php?threads/career-youthplayer-name-groups-tables.183224/
If the tables used for creating youth player names haven't been altered (I don't think they have, sincerely), they now have references to names that are in a different language.
I'll explain it in detail...
- In the "careerlastnames" table, you may see that, say, name #250 is assigned to group 6 (Portugal and Brazil IIRC, you can check it in the "career_namegroups" table).
- If in the default database name #250 was "Moreira" (a tipical Portuguese surname), everything was fine.
- With the modded database, the "playernames" table has been altered (because the team needed to add some names, replace others, and on top of that Creation Master does its own garbage collection on this table) so maybe now name #250 is "Moore" (not a Portuguese surname, is it?)
- BUT... The "careerlastnames" table hasn't been altered, so for the game name #250 (Moore) is still suitable as a surname for youth players.
I've been having exactly this issue for a long time in FIFA 14 (I'm trying to create a career with 100% fantasy players), and the solution I found was to drop these tables:
- career_firstnames
- career_lastnames
- career_commonnames
- career_namegroups
This forced FIFA 14 to look for names and surnames in the "playernames" table instead, but... If the "regen" player was Portuguese, FIFA 14 would only choose between names and surnames belonging to Portuguese players (probably it would join the "players" and the "playernames" tables, selecting a random name and a random surname from players matching the required nationality).
I don't know whether this will also work for FIFA 16, but maybe it's worth a try.