I'm having something similar to this issue. In the faction selection screen, instead of descriptions of the Korath or Drath factions, I get EXP4_FACTION_DRATH_NAME on the header and description section. Once I get into the game, for any faction, I will sometimes get pop-ups of events that are blank with blank choices. The GNN popups will show TopFiveCivNeutral_NewsDescription. Ship descriptions for the new factions are EXP4_FACTION_DRATH_Callsign_Scout-1...Certain Improvements show up the same way as well. I have tried to validate files and they all validate and reinstall. I have uninstalled the game and reinstalled it. Made the entire Steam folder safe from Anti-Virus. Even deleted RebuildData.ini as suggested above. No dice.
This seems to have started right around the time of the new update and I purchased Retribution around the same time as this started happening as well. Do not recall this happening after purchasing Intrigue.