I think I know why it is tilted forward. Back tires are too big compared to how they should be IRL. hence why the harvester is off-balanced
EDIT: it's to do with the restloads of the tires in the xml file, whoever did them completely overestimated the restload on the back tires compared to the front, hence why the back tires have more air in them raising the combine up at the back. I'll do some tinkering and get it sorted for the next update