Everything in your UI's hierarchy (aside from the UI Root object itself) should be a scale of 1. Every parent, panel, widget, and sprite all set to 1. It's a little more work but it keeps everything looking crisp and keeps the colliders and anchors playing nice.
At the bare minimum, you should at least make sure it's scaled uniformly (i.e. - (1.24, 1.24, 1.24) instead of (1.56, 1.24, 1)).
I know it doesn't answer your question, sorry. That's the long and short of it though.