Here's what you need to do if you still are getting distorted meshes after export to .b3d format,
Make sure your armatures don't have any gaps in them. All the bones need to be connected. This can make some types of blender animation harder to do if you're using inverse kinematics, which may take advantage of a broken armature.
Make sure your armatures don't have any gaps in them. All the bones need to be connected. This can make some types of blender animation harder to do if you're using inverse kinematics, which may take advantage of a broken armature.