Ya really weird....
Your base64 file works on the GUI... but the code i get is different from the one I get if I use the binary fsc from e-sys against the NBT.exe generator directly.... wonder if more than one code is valid or if only 1 code works for each VIN
I got my base 64 by taking the binary and using the site
http://www.motobit.com/util/base64-decoder-encoder.asp also but that creates the base64 with those spaces instead of the nulls which then makes the GUI show "fields!!" and not generate the code
The way I got it to work was using the NBT directly like "nbt KS91992_00DE0001.fsc 0xAF 0x02 KS91992"