Quoted from NPO:6. Reinstalled the bracket. I noticed when first taking the bracket off that there were some small circular rubbers (looked like mini post rubbers) mounted between the bracket and the underside of the playfield. My guess is that was to try to align the optos without actually moving them by hand like I did. I discarded these post rubbers for now. Still have them just in case (JIC).
Sega/Stern uses these rubber grommets to reduce vibration to their opto board assemblies. Good thing you kept them!