@vijaynigilesh : Well, I grabbed your file to take a look. No .blend file or Mixamo ,fbx file, just a gltf file. Anyway, I imported it into Blender 2.93 then exported it as a .babylon file . Here is the playground result using that .babylon file:
The animation is just an “Idle” and is kind of slow, so I changed the last number in line 53 from 1 → 1.5 to speed it up. Change it back if you like. Seems to work OK. At 400 frames of animation, it does seem rather long.
I don’t see the issue with the arms you saw in Blender or in the playground.
I will post a couple more thoughts later this afternoon - I have to go walk a dog,
Stay Safe All, gryff 