character won't upload "unknown error"

I've got two 3D models. One has shape keys for the face but a "bad" body, and the other lacks shape keys but has a solid physique. I'm trying to create a model with a good body and a face with these shape keys. Mesh data transfer modifier doesn't work. My plan involves separating the head from the old body, deleting the head on the new body, and merging the head with the body. However, every time I upload the model, deepMotion gives me an "Unknown Error." Any thoughts on what might be causing this and how to fix it would be much appreciated.