Anyone have an answer on how to know the specific problem with an MVS 2 Slot board that gives the error screen "Calendar Error"?

I've done some research and can't find any concrete solutions, though there seems to be three possibilities:

a. The back up battery is dead (needs replacement or modded out)
b. A PCB Rom is dead
c. A connection line (tracer?) is cut

Some entries say a battery replacement is the fix, or that the Unibois would circumvent the check. Anyone know of a sure fire way to know the issue for those of us with no technical experience at all?