MarkC,
after replacing the 2 and 5 rec's and it still does it?
ok, these panels were like that...
first thing i would of done was check the pins and plugs on the card, even go in with some needle nose pliers and tweak the pins in the card with a slight twist to make sure they are connecting. Those terminal pins weren't the best in the world.
Secondly i would have checked the fwd/rev contactor, the 1A contactor, and the RB contactor tips and coils, make sure the tips are in good shape and making good contact when drawn in and out, no excessive wear in the movable tip assy's (notorious for wearing out and causing connection issues). The coils should ohm out to about 10-14 ohm.
THEN i would have tested the #2REC and #1REC and #5REC's (use a handman tester, they work well and can run a leak check to insure there is no leakage through the REC). Normal testing will detect an open or shorted REC but the leakage is always an issue that normal testing does not see.
Also look at the capacitor, make sure it is not swelled up, the posts are in good shape and the connections are good. (please make sure you unplug the battery and discharge it before testing it, i would hate to see you get burned or worse from the accidental discharge from the stored energy from it).
Finally if all of the above does not reveal any issue then go to the motor and cables and insure the motor brushes are good, check the field for shorts to frame. GE book says to check for an open circuit between A1 and A2 connection on the SCR panel.

Note: all these codes are related to the same issue with either contactor problems or bad REC's OR just loose connections triggering these codes.
Unfortunately due to the nature of how these systems work there is no easy fix, you have to check all these things.
If you need any literature on this panel and don't have the factory info you can get it from flight systems (fsip. biz), they have it in their resources section on their website in downloadable pdf format. Pretty sure this panel is a ZX/LX series so find either one of those.