Lost another one

So, last week I had to let yet another temp worker go. This time it was an older gentleman. He showed up to work on time, but unfortunately that is not enough. He was mechanically, and technically challenged (both a requirement for this machine), plus hard of hearing. I tried training him repeatedly on basic operations, but it just wasn't to be. When I tell you not to turn your back on a certain section of the machine, it is for good reason. The reason being I don't want to have to come back and clean up a 30' lake of water, with an eight foot puddle, of now hardening polymer, floating in the middle. And every time I turned around, he had his back to that particular section. If you can't hear if the pelletizer jams, and you can't see it when it jams, HOW are you going to stop the machine?
Not sure how many more temps I will go through, before I find one like my original trainee.
My very first helper was a middle aged, Laotian born fellow, who picked stuff up super fast. And I mean he picked up anything I showed him quickly. The machine type did not matter. Show him once, and BOOM, I could walk away without worry. I had him trained on the quarter-folder, the rewinder, the recostar, all of it. Then upper management thought it was a good idea to transfer him to the meltblown, since he learned so fast. (sad face) He later left our company to go back to school. God I miss him.
Since then I have yet to find one even a quarter as capable as he was. And I should know, I have gone through roughly three dozen trainees since then.