I recently picked up a nice Mary Shelley's Frankenstein that has one annoying intermittent issue. Sometimes when I'm in multiball and drain all but one ball, multiball continues as though the game thinks there are still two or more balls on the playfield. When I drain the last ball, the game kicks a ball into the shooter lane and launches it and then behaves normally from that point. It doesn't always happen, but it seems most likely to happen in six ball multiball (I've never had it happen in Geneva multiball). All the trough switches test fine and I can't seem to recreate the issue with the glass off, only in gameplay. Any suggestions on where to look next are appreciated!