Multiball Stuck Board 4
On board 4, (the one with 6 circles surrounding a larger circle,) as multiball is activated, the main ball can block the extra balls from exiting the onramp, causing them to get stuck and disappear. This is major sad times.
@nitro27 Is this what you're talking about?

Wow, this issue has been open for nearly 6 years? I just experienced the same problem. Yes, that's the table. The existing ball hit the first extra ball back down the chute, which then hit the remaining one, and they both dropped back down to the bottom of the chute and disappeared in short order. The game continued on as if this was perfectly normal and they had just drained.
#149 should fix or at least improve these cases. If multiple balls get stuck they should get random bumps which will hopefully dislodge them (previously this only happened if there was a single ball in play). And if a ball falls back down the launch tube, it should get relaunched rather than disappearing.