Animals tend to back out and panic if they slip. To induce animals to ride calmly in a conveyor restrainer install a solid piece of metal over the top of the restrainer. This metal top must be long enough to block the animal's vision until it's back feet are off the entrance ramp. If animals can see people before their feet are off the entrance ramp they are more likely to rear up. Experiment with pieces of cardboard before installing metal.
Vision controls behaviour in livestock.
Eliminate air hissing and high pitched noise. Pad gates to stop banging and clanging. Cattle may refuse to enter a stunning box if they can see movement under the stunning box door. Install a conveyor belt flap to block their vision. Experiment, experiment with changing lighting, you will be amazed at the effect it has on animal movement.