Quote - I think it is simply that the pose was saved without IK applied.

You can test it by creating two animations of the figure moving its leg side to side. Do one with IK off and rotate the leg. Save as "IK Off". Do another with IK on and drag the foot. Save as "IK On".

Now test each pose of the figure with IK on and IK off to see the results.

hi, not sure if i understand but your suggestion remind me of applying the pose to figure and save as new pose 1st without ik on, then when reapply the new pose doesnt seems to have ik issue anymore. it works at the moment, but strange still, there are commercial n free figure out there which doesnt need to save new pose 1st to avoid such ik issue?