I have seen this all too often.
1. Improper ramps
2. Not securing the ramps to the vehicle, VERY IMPORTANT
Get a good set of ramps, with good traction surface on them; and always tie the off, or bolt or pin them to the vehicle.
I have used aluminum, wood, and steel, no problem. On some trailers I have had holes drilled in the ramps at the top, or a pin or bolt welded to the ramp to fit in a hole at the trailer edge. At least use a ratchet strap to securely hold that ramp to the trailer or truck.
No fun getting hurt loading.
out-there