The playfield mounted diodes are for switch matrix, not for lamps.

And the lamps are not controlled by playfield switches, but the switch is read by CPU, which then lights lamp if needed. If you have problems with controlled lamps, check your driver board.

If drop target switches are not detected by the CPU (use the diagnostic switch test) then there might be problems with some diodes being open. Reset (pull up) all drop targets and then test the diodes with your multimeter diode range. You should see infinite resistance (usually shown as 1. or OL on your meter) in one way, and with the test leads swapped the diode threshold voltage of about 0.1-0.3 volts. Maybe a good idea to disconnect playfield switch cable from CPU board before these measurements. And of course do this with power off!

Yes, the OL both ways definitely looks bad and diode needs to be changed! If you can't find 1N270 diodes, usually 1N4148 will work fine. The nominal threshold voltage is greater, but in the switch matrix, current is so small that the actual threshold is low enough to be just fine.

With low currents, such as in the switch matrix, the threshold voltage is also lower. 1N4148 will probably work but of course the original would be the best choice.