Foot/joint pain can have a significant influence in a horse’s willingness to load/unload. This might very well be a part of the issue for you, BR612. With that in mind, he might always have some reservations about or odd approaches to loading but play around with a few methods, listen to/watch his body language and go from there. Understanding why or why not a horse will or will not comply is a huge aid in resolving most issues.
Sure there's right and wrong but mostly there's just a whole lotta different.