Yup, I can put my money that you didnt copy/past everything correct. Smells like you didnt put descr_strat file in a correct position (last_kingdom/data/world/maps/campaign/imperial _campaign).
campaign_script file goes t same place (last_kingdom/data/world/maps/campaign/imperial _campaign).
Since you can play custom battles I guess you did copy/past battle_models.modeldb file in a correct place? (path is last_kingdom/data/unit_models)... rest of the files goes to a last_kingdom/data.
That is why I sent you a pm k/t, you should have write some explanation for guys who know little about where which file
Nevertheless GREAT stuff you did here (+rep, finally I spreed some so I can rep you again), battles are like should be, everything works like a charm, almost done with Norman campaign, superb! Only one thing tho, notice it in a custom battles (for some testing), you should set Norman knights back to 60 men, that unit is too weak now. 80 for unhorsed knights is good.