I've sold my BG but here is some information for the ball your looking for:
Page 43. Part number: 03-8111-4.
It's a 1" Nylon ball. Off-white.
I originally went to Michal's (craft store) and found a few plastic beads that matched the size of the original. I tested a few of them until I found one that worked. I used that bead for a long time until I came across and actual replacement (sorry, I can't remember who I purchased it from) however, the bead I had originally worked really well.
As for the cannon, I don't think there is an adjustment for this but you might want to replace the coil sleeve and make sure everything adjusted and working smooth. Mine had some mushrooming on the plunger shaft that was slowing it down. I filed it smooth and rebuilt the unit, worked great after that.
Your other issue sounds like a switch problem. Go into switch test and see if all of them are working properly. You may have one that is slightly out of adjustment or has a weak connection.