Best advise on loading a tractor on a trailer is to have ramp set properly before you start up the ramps. Next when you start up the ramps keep your foot (OFF) the clutch until your tractor is all on the trailer deck. Same when unloading, keep your foot off the clutch until the tractor is on the ground.
Loaded and unloaded the pictured load of tractors for over ten years and even the tractor on the back I did not push in the clutch once I started to load on the ramps until both rear tires were off the ramps. It is something you have to put in your head like breathing.