Hmm this is the second report I've gotten about auto-quality in a short time, so I may have to look into this.
AutoQuality's code is just this:
(int)Mathf.Ceil(size * parentCanvas.scaleFactor);
Turns out, parentCanvas.scaleFactor doesn't work when the canvas isn't rendering in screen space. Are you using a screen space canvas?
If that doesn't change anything, what I think is happening is... the canvas is targeting 1080p, but the game is targeting 2160p. AutoQuality only cares about the parent canvas's scale factor, not the game's target resolution.... so maybe the scaleFactor is getting confused somewhere else along the way and I'll have to do a manual comparison somewhere?
First, just let me know if you're using a world space canvas or not, and if so... I'll either have to write a manual scale check, or just say to set the quality manually.