Hi, I had the same problem. I did what some of the others suggested and did load one front foot on and off the back of the trailer a bunch of times, then two front feet and back off, 3 feet and back off a bunch of times, but when he got the 4th foot on he did not want to back off. I did gently push on his chest and pushed him off the back of the trailer and he scrambled a little but then the hind foot found the ground and he learned that the ground would be there. Not a problem after that first push. It sounds brutal but it was not. He just needed to know he could do it and survive. Just like training horses for other things. Sometimes you have to push them beyond their comfort zone. And I literally “pushed” him. And since a ramp is not an option for me all my horses have to learn to load and unload in a step up trailer. Then on my next attempt to load all 4 feet, we worked on walking a few steps forward and then a few steps backward to the edge of the trailer, over and over until he was good at moving his feet in the trailer. I used a verbal cue “step” with the repetitions during the training when they stepped out, and “load up” to step in and now when I go to unload, my horses will back to the edge of the trailer, wait for the verbal cue “step” and then step down.