I like having units with "long traditions" so was looking forward to my "1st Praetorian Guard" riflemen causing mayhem in enemy lines.

Sadly, not sure when exactly, all the customised unit names I've set, have reverted back to their default values.

Same thing happens with army names - they all revert back to "Regiment" or "Warriors".

I haven't pin-pointed the exact moment when this happens but it seems to be related to loading the game or changing the army composition (e.g. removing/adding a unit).

EDIT: I'm 99% certain the name changes don't end up in the save-game data. I just loaded up a save where I had a bunch of names set, checked them, all were default again.