3DS Max morpher export morphing mesh but static normals

I’ve been trying to get a morph animation to show up in Sketchfab for a couple of days now. I seem to have identified some technical challenges that I can’t seem to solve on my own.
Since the feature is a few years old already I’m hoping for some insights and first hand experiences.

The first thing I tried was a progressive morphs. I don’t assume Sketchfab does support multiple morph targets at this time?

The most surprising issue (that you can see in my current morph draft) is one that seems to be consistent across all my export attempts, even for a simple linear morph: The model will deform, but retain it’s original normals. This looks extremely weird. Morphing a baby to an adult for instance will change the geometry, but the lighting on the body will still suggest the baby’s round cheeks and belly and protruding navel etc.
I know this is probably something connected to 3DS max or morpher exports via fbx in general. Any helpful comment would be appreciated!

Best,

Nils Deitmers