Dropping this here for future reference in case anyone is troubleshooting the safe assembly. I recently replaced all of the metal parts, switches and diodes in my safe, but it was still only registering half of the hits. I was pulling my hair out trying to figure out what was the issue, and then I recorded a slow motion video using my phone. I noticed that the entire safe housing was moving around quite a bit after a hard hit. After wiggling the assembly from the top side, I noticed that there was a lot of play in movement inside the bushings where the safe mech penetrates the playfield. I ordered two replacement bushings to see if that was the issue, and turns out the diameter opening on the new ones is noticeably smaller than the ones installed. Not sure if this is due to the age of the nylon, or the constant abuse from the mech hitting against it, but it has made a significant difference. The safe moves significants less when hit, and now registers hits correctly.
You can clearly see the difference in the picture.