Hi Chris, I encountered the exact same problem as 'jodyls27'
When rotating the empty sphere everything seems to run smooth until I run up to 180 degrees on the Y angle; There's a slight jump/glitch which looks odd.
Do you know what is causing this?
The issue is not caused by a logicall loop, as is explained in the fourth video.
After reviewing I found out it's actually a Blender bug. It's the transformation constraint which is causing this.
It's a hardly noticable artifact and it depends on the amount of tread sections used whether it becomes noticable.
This means you can't use this tread system (with a transformation constraint) when going beyond 90 degrees, with other words keep the animation or drive distance short.
Maybe there's an alternate solution?