Sorry,I forgot to mention to make sure your feeder chain isn't in backwards.Brand new combines fresh from the factory have been known to have feeder chains in wrong.That's what I mean about checking everything with a critical eye,and taking nothing for granted.
An air reel really helps in providing smooth feeding to any combine. Another thing to look for especially if your grain head has done alot of work is to make sure your auger flighting has a square edge on it rather than a rounded edge on it. The auger flighting can be redressed with a hand grinder. This can help the auger grab the material easier and move it along.
great to hear you are all having problems in the northern hemisphere as well. Mate has solved feeding problems with aftermarket modification that does not cost the earth. Have tried all the solutions you have posted and found they help in one crop and hinder in the next. Interesting to note our feeder chain was not the only one installed backwards, great quality control! contact stevden@wimmera.com.au for more info. Has sold over 50 in the first season in Australia by word-of-mouth and they are selling just as well painted green as they are painted red