Motion blur on single frames when character and camera are moving together

Motion blur on single frames when character and camera are moving together.

Cannot tell what is causing this. There is no pop in the character animation and the only thing I can imagine is that the camera IS moving quickly through the scene, but not moving quickly relative to the camera.

Occurs on?
4.15 - 3450819 - YES
4.16 - 3466753 - YES
4.17 - 3521650 - YES

1. Open the attached project
2. Go to Developers>[devName]>UDN_motionBlurPop and open the level
3. Open the sequence
4. Select Render Sequence
   1. Render a png sequence
5. Select Render
6. Open the rendered sequence in a image sequence viewer (djv_viewer is what I use)

Result: On frame 115 (20th image in the sequence), the character mesh is motion blurred. The box attached to the character head is not motion blurred and the vehicle is not blurred.
Expected: No individual frames pop with motion blur