IQ7 Input Sharing Question

WebPower

So I've got a technical question and I'm wondering if anyone here has the circuits knowledge that might be able to help me overcome a ground fault error with an Enphase IQ7.

Desired configuration:

300W of solar shared between an IQ7 and a Renogy 50A DC-DC Charger.

Problem:

IQ7 goes into ground fault error when I try to share/hook them in parallel.

Attempted solutions:

Isolate the IQ7 and/or Renogy charger with Diodes

Place DC-DC power supply between panels and IQ7 or the Renogy.

Why do I want to do this?

RV has 900W of panels installed. I goofed and didn't realize the Renogy will only take a max of about 300W of solar input. Also, I've got spare capacity and want to have the Renogy keep the engine battery topped up while also using the excess solar capacity to feed back into the grid. Once the engine battery is at float, I'd like to automatically utilize the solar to feed back to the house grid tie. So I really only need a little bit of solar power to be supplied to the Renogy. Most of it would be fed back into the grid.

The other 600W of solar has been dealt with as it supplies the grid because the RV has a Magnum Inverter Charger that keeps the house batteries topped up so I don't need the solar when parked at the house. I manually switch between an IQ7 in the driveway and the RV's Renogy Rover MPPT charger when on the road.

I've been trying to find an isolating DC-DC power supply for a reasonable cost (~$50 or less) to try, but I haven't been able to source one. I don't want to buy one for $200 and have it do the same thing so I'm hesitant to buy a more expensive one.

Thanks.

Pat