Turmoil and outright persecution that took place in the first centuries of the Church in the East over precise terminology and application of theology.  This contributed to the name given Orthodox Christians: ‘right belief’.  This adherence to correct dogma continues today.

While few would really consider the ‘Great Council’ of 2016 a ‘council’ since the numerical majority of the Orthodox jurisdictions didn’t participate including Russia and Antioch, one of the documents has stirred so much controversy that some priests throughout the world and a growing number of cells on Mt. Athos has stopped commemorating the Ecumenical Patriarch since they regard him as promoting heresy.

Specifically, referring to non-Orthodox bodies (i.e. Protestants, etc.) as ‘church’ is seen as clearly departing from traditional Church teaching and sends a false impression that there are different ‘parts’ of the Body of Christ.  Here is more information for reference…