Here is a screenshot in Unity, as you see those 3 parts all have the same incorrect scale & rotation. Usually fixed with Cntrl+A & apply Scale, Rotation. 'female_nude_base' has a scale of 1,1,1 & rotation of 0,0,0 which is correct.
I fixed the head and base scale, by using the apply method above. But the RIG is still incorrect, I cant seem to apply the scale in blender for it.
Hmm ok I'll have to look into that. I was using rigify for the models, but only because it's free with blender, I actually use Auto Rig Pro (which is amazing!) But I don't know if it's legal to sell models that use it and I also don't know if the rigs will work for everyone but if they do I'll include them in the future.
In the meantime I found this video that should hopefully be helpful
