In every stance besides "standing" and "crouching" your legs wont move if you are turning left and right.
It seems as if your soldier is hovering left and right.
But while turning left and right in stand up and crouching position - your soldier will move its feet like its supposed to be.
It seems to be unfinished yet.
This looks especially bad in the lower and the upper prone.
Also: The reload animations for the pistol doesnt look right whilein the upper prone.
Here is a video of the issue.
An idea for the upper and lower prone:
Upper prone: I suggest you make the legs only move after the soldiers looks away more than a radius of 120°. Before that the torso simply can turn left and right without the legs needing to be moved.
Lower prone: Let the body be fixed to the ground - only the upper body arms and head shall be moveable in this position in a radius of about 45°.
When exaggerating this radius the soldier should automatically return to the prone position and try turning its body. This would prevent a mircomanagement heavy control when you have to quickly react to a danger 90° to you.