Hey there,
My GUI stays in the center of the screen when my screen is a square, but when I make my screen a rectangle the GUI moves off center.
Both size and position are entered in under scale, nothing is in offset. The large shop frame has a UIAspectRatioConstraint.
Thanks for any and all help 
.
Make the UI.Position for the big shop frame 0.5 and make the AnchorPoint 0.5 for X
that should make it work properly
Wow, thanks for the help, that was super quick and kind of you to reply! Everything is working now.
Happy to help, I honestly would’ve responded earlier but I just leveled up to be able to reply lol