Looking at your post here:
https://forums.autodesk.com/t5/autocad-for-mac-general/autocad-for-mac-user-give-them-your-feedback/...
I realised that your problem with "shifting us" could be:
- if you are using Trackpad - you may accidentally touch Trackpad surface with two fingers when Shift key is pressed
- if you are using Apple Magic Mouse - you may accidentally touch Magic Mouse surface with two fingers when Shift key is pressed
-if you are using mouse with scroll wheel - you may accidentally press on the middle button or touch scroll wheel (ball) when Shift key is pressed

All operations above turn on transparent 3DORBIT command and you rotate view direction in the viewport. USC is not affected by this.

Maxim