What I am saying is that when you get a A9 light to come on, its not always a "real" fault. If the A9 turns on a fault light, and your the set runs, and you can still close CB2, and the output is right, then the "problem" is normally in A9. In your case, you needed to flip the S7 up to get the CB2 to close. I would say its a 99% chance its K15. Since you probably do not use the parallel function, K15 is not really needed. The way you and Scobby "fixed" it is what I would and have done, until I could order a new relay.
The normal A9 fault is when anyone of the lights comes on, but nothing stops working. You can reset the fault light, and it will come back on. Sometimes a mili second later, sometimes 1-2 minutes later. I believe the part in the A9 that fails is a SCR. There is one per light. If you really want to know, go to the -34 TM and there is a breakdown of the A9 electrical circuits. They are not in the normal wire diagrams/schematics.