Why is my ancestry not correctly assigned within the Central European or Balkan region? 

Central European countries are a unique example due to their recent history. Due to political phenomena, mainly the two world wars, the countries of Central Europe have a rich history of migration, which has led to a significant genetic mixing between the surrounding regions. For this reason it is difficult to differentiate with precision the ancestry between some of the countries that make up this group, mainly between countries such as Germany and France. In these countries, individuals from western Germany may have a strong French genetic component and individuals from eastern France may have a strong German genetic component, which can lead our calculation algorithm to small errors. 

The same phenomenon occurs in the Balkan countries where, until recently, some of what we now consider as separate genetic populations were part of the same country.