Not saying there is a bug, I don’t usually fly with 100% fuel, but here’s a tip.
Occasionally, when I'm launching out of a particularly tough field or want to change course immediately after launch, I'll leave the gear down, climb to 200ft agl and begin a sharp turn. The drones will follow like baby ducks chasing their mother. Once you’re on course, set auto climb, reduce throttle 15 or 20% and raise the gear, this will initiate normal formation keeping.