After exporting an animated skinned mesh from Maya using the Three.js exporter, I noticed that there is always a duplicate mesh combined with it that remains static and not animated.
Despite trying various export settings and ensuring that no other mesh is being exported along with it, the issue persists. This problem can be replicated by skinning, animating, and exporting any mesh.
I carefully examined my exported .js file but couldn't identify any noticeable differences compared to a functional three.js example like this one: