Clogging?

[Unglued]

So, many shooters are gravity fed, and some use an elevator, but if the balls don't come in a nice single-file line, how do you stop clogging without using up any more vectors? if you have funnel, there's bound to be a time when 2 balls get stuck/clogged, does a quick shake solve this? how do (if you can) avoid this, and how common is it?

pictures will be greatly appreciated