@FBJ Were you ever able to resolve this problem or work out why this is happening. Ive been struggling with the same issue on multiple sites.
Im now dealing with sunsynk support who are also not seemingly sure on why this is happening. Im getting odd type of reasons such as the inverter uses the voltage on the terminals to determine when batteries are full. That does not sound right to me as different batteries have either 15 or 16 cells meaning different voltages. It should be using the SOC from the BMS to determine SOC and therefore when to export.