Yeah. I have two hands with one armature each and they animate and work fine in blender. However, when I import them into unity this happens:
This is what they look like in blender for reference.
Anyone? 
I’m sorry but I’m not a blender user (you’ll have to wait a while longer for one of those to post)… but… I sometimes get similar results when I export stuff with animation frames from modo. I cure my problem by making sure the model has been triangulated prior to export. are all your poly’s triangles when exported? I convert all polys to triangles prior to exporting.
Like I said, I’m sorry I can’t help you directly, but it maybe worth a shot until a blender user comes forward.
Best of luck and many regards,
Matt.
Okay, thanks anyway.
Do you get any errors/warnings in Unity when importing?
Looks like you’ve got un-weighted vertices. Before exporting a rigged character, you have to make sure that each vertice is 100% weighted to a bone, otherwise you’ll see weird stuff like this.
I agree, this is usually the effect of un-weighted vertices. Note that this means not to use Envelopes for the armature deform options, but only Vertex Groups and weight painting.
Hmm… I did use weight painting for this and I thought every vertice was painted. I’ll try and select them with vertex groups instead.