battlesuit.blend contains two skeletons. BattleSuitArmature is animating the suit (specifically the mesh named Core), PilotArmature is animating the mesh named Pilot.
When exporting battlesuit.blend, using the latest Blender exporter 3.0.2, the .babylon file contains wrong skeletonID references. The skeletons are:
"skeletons":[
{"name":"BattleSuitArmature","id":0,"bones":[...],...},
{"name":"PilotArmature","id":1,"bones":[...],...}
]
Yet the skeletonIDs referenced by the meshes are 0 for Core (correct) and 4 for Pilot (incorrect). The pilot's skeleton is not even loaded by BABYLON.SceneLoader.ImportMesh. In the callback function, Skeleton[] has a length of 1. When I change the pilot's skeletonID to 1 in the .babylon file by hand, everything works as expected.