The error looks like it's in the unit_prod file. When loading the unit file, it came to an entry for an STW_Ashixbow that it doesn't recognize. Unit names are initialized in the /loc/eng folder in the names.txt about 2/3 down in the file. You'll see the unit names down there and also the singular/plural names. If you've added a new unit name to the crusaders_units_prod11.txt or whatever file you're using for your units, then you also need to add it to the names.txt in the appropriate places. If it wasn't a unit that you added, then it seems like that might be from a mod. Did you recently install the STW mod?