When your driver's actual path appears erratic or scattered, this usually happens due to one of two reasons:
The most common issue is that the driver was driving this route rather than the one suggested in route plan
GPS tracking issues rather than actual driving patterns: The other cause is phone location permission settings that restrict background tracking. If driver's phone is allowing location only when Upper app is open, this might cause issues. Update the settings for this.
To resolve this, ensure the driver's phone settings allow location access for Upper even when the app is running in the background.