Hi guys @Rosh - Quantum Solar @Coulomb @Trick720
Same issue here with Axpert max II 8kva.
Often during the night in SBU or SUB mode when batterie level is low the circuit breaker of the AC Input is kicked off. The default "line fail" is reporter on watch power app.
A little while after, when battery reaches the cut off voltage, the inverter stops and default "low battery" occurs, which is normal.
I also suspect the grounding but dont know how to solve it.