Using Blend Physics Weight causes skeletal mesh to spin at high speed

When Phyics Blend in the PHAT editor is set between 0 and 1, the user character will spin wildly. User has image of this affecting character in game whereas I was only able to replicate it in the PHAT editor.

Files provided by user available upon request.

1. Open up attached user files (Project: Oktomari)
2. Open Physics asset: "Oktomari02_phat2
3. At the root level, set Physics Blend to any value above 0 and under 1.
4. Simulate.
5. Observe: character spins wildly out of control.