STEPS TO REPRODUCE
1. Launch iClone 6
2. Apply a character with spring effect
3. Go to any frame, click "Parent Rotate" on toolbar, rotate the character
4. Go back to frame 1 and click "Play"
5. Navigate to Modify > Edit > Avatar > Avatar Proportion > Scale, drag the slider of Length to change the value
6. Repeat Step 3 & 4

ACTUAL RESULT
The spring lost effect

EXPECTED RESULT
If character with spring effect, change the settings of Avatar Proportion, it will still have the spring effect