Folks - after the fuse fix the inverter has been operating normally. Today at 20:00 when AC power disappeared the inverter shut itself down (for no good reason) and had to be manually restarted. 
It has been in service since April 2021 at a customer and has performed flawlessly. The present batteries are 4x Narada ND200 and are connected in series. The battery selected is AGM. 
Would be grateful for guidance 

Vaughan 

 

Doesn’t show too much detail - here is a Recent page from Watchpower