The food reward is too sticky thus sticking to the cup: It was definitely not that the food reward is too sticky. Almost all of them would fall out of the cups.
However, I had an Aha! moment when I realized that the food rewards that didn't get dispensed properly are small pieces of craisins. WEIGHT! It was weight. I need to have craisins that have enough mass to fall from the cup as soon as it drops down and accelerate into the chute. I bought some "whole craisins" which are basically craisins from whole large cranberries instead of varying sizes. I'm happy to report that the food rewards have been dispensing properly today.
Size and weight do matter when it comes to being dispensed properly in my apparatus. Have I mentioned how much they LOVE craisins?