You must be mistaken. There is no way you got 3800 feet in a wifi congested area. Anyway, have you tested one of your other Solos that gets more range at the same location?
If one Solo is outperforming the other, then you should probably check things like antenna orientation and battery charge level in the controller. Then you should compare params. It's possible the Solo that is returning to launch early has different fail safes or geofence params. You'll need to use Mission Planner or Tower to check.
Checking params is pretty easy. Just search within the params for "fence" and "fail", then note down the numbers and compare against your other Solo.