MPP LV6548 RV Open Ground

[Ozark]

Sorry to post a question I know has been hashed and rehashed for years now but I can't find a straightforward definitive solution, so here goes...
This is a travel trailer install, will use shore power, PV, genie & batteries
MPP LV6548, (mfg date prior to March 2022) original firmware
N/G bond screw REMOVED
2x EG4 48v 100Ah batteries
1200w PV
trailer inlet hardwired to MPP 6548
MPP 110v out wired direct to trailer load center

In operation:

• 110v shore power via trailer inlet through MPP = all good
  (prior to removing MPP internal N/G bond screw it would trip "on-shore" GFCI)
• 110v generator using N/G bonding plug via trailer inlet through MPP = all good
• Inverting from batteries or PV gives good power but no ground

When inverting from PV or batteries 110v trailer outlets show open ground and varying potential neutral to ground

Pretty sure this was not the case prior to removing the internal N/G bond screw - which I removed because of tripping the on-shore GFCI. This is the case whether 48v-12v converter is connected or not.

Shouldn't the MPP unit's internal transfer switch handle switching appropriate ground config automatically?
Is there possibly a simple setting to correct? Or firmware up date (and which one?)

If you have experience with this situation please help.

 

[Ozark]

Or, short of the MPP unit ever operating correctly, could I wire a 30A switch in the A/C out line that selectively bonds or un-bonds the neutral and EGC?

This is less than optimal in that I'd need to remember to set the switch correctly for each different site and condition but at least it would function somewhat properly.