The Header is leaving grain on the head?
Speed up the stripping rotor also check fingers for wear

The Header is tearing the complete head off?
Slow down the stripping rotor

There is excessive Header loss?
Slow the rotor speed and increase ground speed

The auger is plugging?
Check there is at least 3/4” clearance under the auger

The combine is not feeding smoothly?
See if the adaptor plate can be adjusted to reduce the dead area between the feeder chain and auger

Lower heads are being missed?
Lower the Header and raise the crop deflector

Grain can be seen shooting out from underneath the front of the crop deflector?
Lower the Header and/or the crop deflector