You are 100% sure SW57, the bumper lane opto for thing flips is working? Roll a ball over it again to be sure. All 5 optos in a column out at once would be a common problem. Four out of five does not seem common.
If for sure only the 4 bookcase optos are effected, the only real logical causes are either loss of ground to the LEDs or loss of 12v supply to the receivers.
If possible put a voltmeter on dc volts on the LEDs. One connection of each LED should be zero volts (ground) the other 1v to 1.5vdc. This gives you the volts across each LED to light them.
Check volts on all 4 receivers. Volts should be 12vdc on one lead of each, the other lead will toggle from zero to 12v depending on whether the opto beam is blocked on not.
If all this checks normal, procede to the 7 opto PCB and make sure all wiring there toggles the same way for each opto. Two different LM339s are used on the board for these four opto switches, so seems to me it's not the 7 opto board most likely.
The most common thing would be in reality all 5 optos are not working, and in that case it would be the wire from the 7 opto board that is column 5 is broken off one of the other non-opto column 5 switches on the playfield.