Heres your problem, in scripts/ships in the UssGriffinExtended script is telling BC to look for the model in the wrong place.
The script should look like this:
                         "FilenameHigh": "data/Models/Ships/UssGriffin/UssGriffinExtended.nif",
      "FilenameMed": "data/Models/Ships/UssGriffin/UssGriffinExtended.nif",
      "FilenameLow": "data/Models/ships/UssGriffin/UssGriffinExtended.nif",
NOT like this:
                          "FilenameHigh": "data/Models/Ships/UssGriffinExtended/UssGriffinExtended.nif",
      "FilenameMed": "data/Models/Ships/UssGriffinExtended/UssGriffinExtended.nif",
      "FilenameLow": "data/Models/ships/UssGriffinExtended/UssGriffinExtended.nif",
So just goto Scripts/Ships, open UssGriffinExtended and delete "Extended" so that it looks like the top example.