No. That configuration should be bullet proof. Are you sure this is only a 8kw unit.. the guts look more like 10kw..
Anyway, that fet destruction is normal for when you have a signal failure or fet failure. They are caught between the battery potential when they short... either they blow your battery fuse ( will happen if a few short together at the same time) or they will simply explode to get rid of the short.. fets always fail short, as you know what happens with a screwdriver across the batt terminals... well thats what the fets try to do too.
When one fails first, and explodes, then the next and the next follow in a cascade of pops, until there is no fet trying to short the battery any more. If they short together, then they have enough "fet legs" to present a massive low impedance, and then it may short your fuse if you have one.
Something was wrong with it. It should have saved itself from over load.... and the loads you describe would be trifling for it.
I have no idea of what split phase would do to the current ratings or how it works with the CT... we don't have that here... thats the only complication I can't guess at.
Usually it is something like loose battery cables, terminals even... then any other thing you have in the battery line that could cause sparking and inductive problems.... check the ribbon that connects the two boards together for broken wires, unplugged, and the opto isolators are plugged in properly
So no, I don't know how or why it failed.... as I don't know how the current transformer sees the loads at 110v and 220v..... totally unknown at the moment.
The charger needs the frequency and voltage to be in range.. if you know it was in the right range ( grid perhaps), and it still would not sync, there was something wrong with the mother board.
..oztules