I am terrible at designing GUIs, but I had to use a UIAspectRatioConstraint to make the BulletPositionFrame square.
Usually, I just use Scale of Position and Size and set Offset to 0 and everything is fine, but the UIAspectRatioConstraint breaks the GUI’s positioning (Setting SizeConstraint to RelativeXX or RelativeYY is even worse by the way)
Have you tried putting the AnchorPoint to [0.5, 0.5], then repositioning back to it’s original position?
It usually works for me. If not, then I cannot help in this type of situation. Sorry.