Harmut, do you have the Alde connected through AC2? If so I suspect the load is too great for the transfer switch possibly? I use AC2 for fridge, 1 Aircon, 24vdc charger and washing machine only. I have the Alde outside the Victron AC1 or AC2, and feeds directly from EHU in and I have the Alde load monitor.
Just a thought on reason for failure of AC2?
Michael