I think is the "bug" destruk talked about many years ago about the visible lock, which sometimes didn't work as planned.
The poles in the locks are just decoration, the ball will never hit them. The kickers are the ones which stop the ball.
The visual lock was developed so many balls could be locked without slowing down the table. If I used a simple pole to stop the ball then the whole table would become unplayable when a few balls were locked due to the continuously ball collision events. I guess tomorrow will be a "hard core test day" and I'll see if the bug comes up. It has happened to me before, so I know it happens (and I have learned to shoot the middle lock from the left flipper, so it will be easy to test )