After the June 2023 patch, the third mastery achievement for some civilisations is broken.
For example, for Mongols, the third mastery achievement now reads “Mastery_Mongol_03” instead of the achievement name and no longer shows what needs to be done for the achievement.
Same Happening for Ottoman, Abbasid, Chinese civilisations, all for achievement 3.
Happening on PC, Windows 11. Just started Mongols, so have no current Mongol achievements.