Hi, I have 2 x 5KW Axpert inverters. Just bought a new 10.5 KW Revov lithium battery pack. I installed it myself and as soon as the batteries supply the load by themselves the inverters cut out and give me an error 72. The voltage output is not stable, it jumps up and down. When I put one inverter of by the off switch, the voltage is stable at around 230. Please can someone help.