more turnout, less heating food, keep net full and some stable toys and/or another horse that can be seen or even touched, basically it is a vice due to stress - so by stopping it from cribing on the door, it is just going to keep its stress inside not healthy so might resort to another vice. Difficult one
As I have said in previous cribbing posts I think it gets to the stage when it becomes habit rather than stress. My pony has done it for over 10 years and is certainly not stressed now, we have tried everything to stop him doing it. As for a recipe we have tried mixing curry powder and mustard together - he liked it! Marmite and mustard - he liked it! Cribox and mustard - He liked it! If you come up with anything do let me know I'd be glad to try it on him.
Obviously, management is the key (especially ulcer and feed related stuff) but I think it's worth painting any exposed wood work, just to remove temptation, if you're doing everything else to make the horse comfortable. I've had decent luck in the past with either dish soap (washing up liquid) and cayenne pepper or vaseline and cayenne, although that makes more of a mess.