The issue regarding gradients

[WZDDZFJ]

I have a question about the gradient to ask you in DAFoam. On a two-dimensional airfoil, when it is not deformed, the gradient values of the FFD points symmetrical in the wingspan direction are very close. I can understand this. But why do they obtain different gradient values after synchronous deformation (that is, the result of calculating the gradient after the second time)? I can't understand this. They have exactly the same amount of deformation. Why are the gradient values after deformation significantly different ？Is this because "Create linear constraints to link the shape change between k=0 and k=1" is set to ensure the synchronous movement of the FFD.
This issue is very important. Thank you for your reply!!!

[hzrssb]

I also have some questions. I would like to consult all the experts.
@JustinSGray @ewu63 @jrram @lvzhoujie