upload fail; "Unknown Error"

I have two 3D models: one with shape keys for the face but with a poor body, and the other without shape keys but with a good body. I'm trying to create a model with a good body and a face equipped with shape keys. My approach involves separating the head from the old body, deleting the head on the new body, and merging the head with the body. However, with each attempt uploading the model, deepMotion issues an "Unknown Error." Any ideas regarding possible causes and solutions would be highly appreciated.