The shoulders, the constant pressure he has to apply throughout the movement, the overhead reach then pressure in a way that is at the bodies less than ideal situation, also the number of repetitions per hour, at four hours or more per day will assure some physical therapy down the road.
Now, if he could implement something that amplified his downward force, that would help considerably, a cam perhaps. I'm not a mechanical engineer, but there must be ways to ease the operators effort.
Production lines in factories are a great place to find out what causes long term injury, and there are plenty of rotator cuff issues that can/will arise with that lever the way he has it. Hydraulic operation with a manual override option would be the best setup in my opinion.
Two cents...