You might want to check to see if the balls are magnetized. I just ran across this exact issue on a TOTAN. Even got to the point of replacing the trough. While standing in front of the machine and totally frustrated, I happen to glance down on the lockdown mech where all the balls were sitting. That's when it hit me to check for magnetism.
Replaced all the balls and the problem went away.
Sometimes simpler and cheaper options are more fruitful.
Good Luck