Altered Game files, Britannia campaign now has an unspecified error

[Asiriya]

Have tried to install the real combat mod for the britannia campaign, have set up the shortcut to get it to work. I was getting the UI glitches so I unpacked the M2TW files which fixed that and everything seemed fine. Tried to fight a battle and got an unspecified error. The log is saying there's loads of stuff missing but obviously not what the actual error was.
I tried to do a little modding previously, of export_descr_unit, with similar results. I replacedthe original and the game started working again. I haven't however touched the RC files. Not sure why the game is so unhappy with me altering the files, especially as M2TW let me do it fine.
Help will be much appreciated.
EDIT: Ergh, feel like a fool, forgot to get rid of geography files.