Adjustment to coil bracket on Trough mechanics from factory can case miss count to ball's in multiball mode.
This was discovered during Ambush multiball, when there is 3 balls in play and only 3 in the trough there is not enough weight from the 3 ball's in the queue to push them over the coil shaft tip that is mounted to high.
To check if you have this issue:
Power off machine.
Take off lockdown bar.
slide out glass.
take out 5 ball's by pushing the trough coil shaft up wards so ball pop into shooter line, pick them out one by one.
leave one ball in there for now.
take a pen and gently move the ball backward and, let go, if it stops on the coil tip like image.
If last ball is stopped by the coil shaft tip, like on image. You need to adjust the coil bracket on trough.
to fix this you need.
1. Multi-Bit Screwdriver.
2. Torx bit T-20
on the trough mechanism we should only need to loosen the 6 T-20 screws (1 - 6)
Check that the trough adjustment bracket with the coil bracket on it are now both loose.
adjust the main adjustment bracket all the way down and let the small coil bracket follow.
Tighten down all screws aging. Your trough should look like this now:
If you had the ball still in there, you would also hear it settle in correct position.