Thanks! Looks like the problem had to do with passages that had no links whatsoever (which coincidentally were the Twine.image ones). It's not too hard to add an option to skip them and maybe throw in options for other tagged passages to be skipped as well. However, even after that addition it looks like for this project in particular there are other possibly non-standard characters that would cause problems with the decode as well as custom macros that wouldn't make this a simple conversion.