Firedog
concerning your experience with sense boards, needed or not.
well
processing board of batt electronics is governed by brain - PIC 16 chip into which signals from sense boards are fed.
this chip has registers which are cleared or not depending on situations , resetting PIC can be partial or complete, there are several types of resettings for PIC.
I dont see connection between sense boards and ERROR 1 so maybe coincident?
It might looks like you dont need sense boards when PIC already registered values from sense board and holds them.
but when full reset is executed PIC "expect" signals from sense boards and it will not allow for power up without them.

I dont have EPLUS schematics and all I know this from PIC datasheet which has over 100 pages /!!!!!/
written in tech jargon I dont understand all of it.
So I know ONLY that much.