I personally researched this when I was at Bally in the 70s. We invested in a Polaroid super-slow-mo instant 8mm camera projector, which was SOA at the time. This allowed Desi D' Percel and myself, actually Desi did the work and I watched, to examine the way targets reacted when hit by the ball and learn why they didn't always fall. When slowed down we learned that when a ball hits the target head on at fast speed the top of the target bends backward into the rubber behind it and bounces back forward before the spring can pull it down. There was no real fix for the problem without a redesign or finding an alternate material to make the targets out of. Any redesign could potentially infringe on Gottlieb's patents so the only fix implemented was adding a ledge to the top of the target.

Best fix I know to this date is to replace the targets and springs with new parts as the legacy parts are probably worn and dried out.

Far too many to list here. As time goes by I chip in whenever someone revives a memory.

Unfortunately there is no tried and proven fix for Bally DT bricking. If the targets and springs are new just enjoy the game as it is what it is. If anyone comes up with a documented fix for Bally target bricking please post it in a new thread.

Gottlieb owned the patents. Bally was limited in what could be done with their available tooling. It was decided the targets worked well enough as-is. If anyone would like to embark on an upgrade project I would start with Gottlieb and reverse engineer. Just don't infringe on any active patents that PBR controls.