There is a bug in national leagues
A friend is playing with switzerland and he has Manuel Akanji in his squad, everything normal up to there. On the other hand, I am managing Netherlands and in the transfer market I bought same Manuel Akanji from Borussia Dortmund. So now, we have two Manuel Akanjis in the same Leage. When I first noticed this, I started looking for the same errors in other squads and, for example, Portugal has two Rui Patricios.
I really think that you should dissable the transfer market system from national leagues. Instead you could allow managers to have access to all the national players. Personally, I do not like having the possibility to buy any player like Ronaldo, Messi, etc. if they are not from my national team.
I wish you could do something about it, that way, the game would be more realistic, enjoyable and competitive.