Ladies and gentlemen; for anyone facing these bugs, (Bretonnian Errantry War dilemma not triggering even though player reaches the required chivalry and Repanse water mechanic/chivalry/peasant economy not functioning as intended) here is the solution:
*First of all these bugs occur because of some previously installed mods that edit start pos files that leave ghost files behind even when you unsubscribe from the mod or delete through mod managers and creates a conflict with the latest Bretonnia update which is the Repanse the Lyonesse FLC.
To solve this do the following one by one in order:
1-Unsubscribe from all the mods through Steam.
2-Delete all the files in your steam/steamapps/workshop folder.
3-Delete all the files in your steam/steamapps/common/Total War Warhammer 2/data folder.
4-Go to Steam library, right click Warhammer 2 Total War, go to local files and click verify the integrity of local files. This will lead to a download process of about 30-40 gb and replace all the corrupt/ghost start pos files left behind from previously installed mods that clash with the Repanse FLC.
And there you have it. This should fix the bugs.
Have fun, take care