Walt, I don’t use O-27 track, so no experience with it and milk cars. However I think I might be able to help. Looking at the end of the platform you can see an outer tab and an inner tab. The inner tab, closest to the platform has a slot in it.
If you make sure the side of the track closest to the platform fits into that slot, that should put the track in the right spot. When I tested it, the doors did hit, but still opened enough for the man to push the cans out.