I was looking through the exporter code and there appears to be an issue if the animation doesn’t start on frame 0. The animation range is then incorrectly set as starting from 0 instead of whatever the offset is. The fix is pretty easy and makes it so we don’t have to modify the babylon files manually.
To fix the scaling issue I download the mesh from Mixamo and delete the armature so that only the mesh is in the file then scale the mesh by 0.01. You can then reskin the mesh in Mixamo and when you follow gbz’s tutorial the scale is correct so you don’t have to do it in the engine and all children won’t be scaled funny.