STEPS TO REPRODUCE
1. Launch iClone 6
2. Navigate to Menu > Create > Surface > Plane
3. Apply prop Arc_002, press E on keyboard, rotate the prop by 45 degrees
4. Navigate to Toolbar > World Move, choose Local Move
5. Go to Modify > Physics, check the box for Activate Physics and select Rigid Body, click “Dynamic” Button
6. Go to Modify > Initial Force, select “Local”
7. Go to Modify > Edit > Transform (T) > Move, set Z to 800
8. Click to play
9. Pick the prop, go to Modify > Initial Force

ACTUAL RESULT
It's changed back to “World”

EXPECTED RESULT
It should still be “Local”