This happens because scaling also "scales" the offsets in relation to the anchor. Depending on the kind of anchor.
That's why scaling isn't the necessarily the best way to change the size of an object/frame. It's better to change height/width, directly and to use anchors that make the most sense for that particular frame.
If you are comfortable with the default UI, you might consider taking a look at Neals
Neav UI. It recreates and enhances the defaults UI look.