You might try using BVH file as an alternative (see #60 for detail):
export the animation to BVH file from Blender.
import the BVH file into Blender, then export it to VMD via mmd_tools panel.
parenting the charactor mesh object to the BVH armature object and [Convert] it to a new MMD model via mmd_tools panel, then export it to a PMX file for playing VMD in MMD.
When I export an animation from Pokemon Sun, Moon, Ultra Sun & Ultra Moon, this happens in MMD. Is it possible to fix this