Found that M&B switch on the Lite Center Target relay, it was adjusted properly. I've found that the Lite Center Target relay doesn't energize at all, ever. But when I activate it manually, the 300 point center light comes on. The Center Target relay is adjusted properly as well.
Also, the two lower pop bumpers which share both common and hot wires, do not light ever. But the upper pop which has a different common, stays on all the time. All three are supposed to give 10 points, and then 100 points when lit.
I found the schematic on the IPDB, but it's tough to read and therefore impossible to know which switch to check on the score motor.