For what it’s worth: I deleted the dll that came with Leafcutter [1], and replaced it with the one from the ArchiCad-GH Live Connection, which seems to resolve the problem. That said, these assembly conflicts do seem potentially quite problematic.
[1] I will be looking into implementing the newer Google API’s (.NET and Python) for communicating with Google Sheets, so if anyone has any experience with these I’m all ears 