Notice how I fiddle with the properties of the UIAspectRatioConstraint and how the frame being constrained does not get re-centered. To re-center it, I have to use and un-use the emulated windows.
This happens in engine as well as Studio. Putting this LocalScript inside the frame with the UIAspectRatioConstraint:
while true do wait(1) script.Parent.UIAspectRatioConstraint.AspectRatio = math.random(1, 9) / 10 end
…produces this effect.