Hi All
Thanks for the replies,
The root cause is simply Humidity, combined with the coast. The PCB,s inside the inverter were so rusted!
I have since replaced with another growatt and I have also provided dehumidifiers into the inverter room, running a few months, no water or rust on the inverter so far.
Please be careful, this is an expensive exercise.
Happy installs,
Best Regards,
Curt