Trace Elliot manufacturing, what were you thinking?! Expensive looking collet knobs on splined potentiometer shafts. They didn’t even put little shims in the slots as I have seen some manufacturers do so the slot closes up. The knobs just go on wonky and come loose so you would be paying for this lazy solution when the warranty claims start rolling in.
By the way folks. Don’t ever try to prise the slot apart, the metal breaks so easily and you end up paying for a new potentiometer. The only technique I found to get them to stay on was to give them a really good tighten with a good driver and hope for the best.