48V EG4 WallMount Indoor 280Ah battery with Sol-Ark 15K having F20 errors

I have three EG4 280 Ah batteries connected to a Sol-Ark 15K with 13Kw of solar panels.  Batteries are installed in the garage and a split mini heat pump keeps the temp above 50 deg F in the winter and below 80 deg F in the summer.  During the winter the system goes for months without an F20 error, but as soon as the longer days show up in spring (late February, early March) the F20 errors begin to reappear every three to ten days.  Nothing new is running to cause the error.  Sol-Ark says the batteries have problems working with their inverters and that the F20 error is caused by out of spec voltages while the EG4 batteries are charging, and EG4 says the batteries will work with Sol-Ark inverters.  Sol-Ark refuses to add the EG4 batteries to their list of "Battery Partners" due to problems reported by users.   The contractor has tried to fix the problem several times without success.  I'm wondering if anyone here has had a similar problem and has any suggestions?  The system is closed loop, and, as far as I can tell, all settings meet EG4 battery requirements.  Other than the F20 issue the EG4 batteries are great, and the $/kWh is excellent.  I can live with the F20 errors cropping up every few days, but would very much like to eliminate them if possible.