Bump Offset Decal Attached to Rotated Parent

I’m using bump offset in an emissive decal material to create a parallax effect. I want to be able to parent these decals to a static mesh so that they move and rotate along with the parented mesh. Unfortunately I’m getting weird results in this case.

Is there anything I can do to make a bump offset decal look correct when attached to a parented mesh?

I made a short video illustrating the material and what is happening.