The Achilles heel of any pellet dispenser is pellet jamming.  There are several reasons for a jam, but one of them is that the pellets inside the hopper align in a way that impedes the movement of the dispensing disc.  To combat this issue, I've modified the stepper code to make the stepper "vibrate" while dispensing.  This can help shake up the pellets in the hopper and reduce jams.  

Please leave feedback in comments if you try this update!