Quoted from ita47:Thanks for all the reply's. I don't remember BSD having trough optos, pretty sure its only switches, but I don't have the game in front of me. We replaced the trough switches two years ago when we go the game. It could be one of those is flaking out. We also recently replaced the 10-opto board under the playfield with a new one from Homepin.
I used to have the exact same issue with my old BSD. It was a worn out shooter lane kicker arm. Replace it and clean the trough mechs well