Where is the save file, and why send it?
The mod keeps a trail of what happened in your game inside the save: the pages you opened, the choices you made, the people you spoke to. With it I can usually see the fault at once. Save the game after the fault, if the game still runs, and send that save. After a crash, send the last save you have.
Your saves are in this folder:
In it there is one folder for each mod. Open the one for Warband Reimagined and pick the save you were playing: the files are named sg00.sav, sg01.sav and so on, and the newest one is the one you saved last.
After a crash the game's own log helps too. It is the file rgl_log.txt in the game's folder: in Steam, right-click Mount & Blade: Warband, then Manage, then Browse local files. Send it before you start the game again, because every start writes a new one.