And obviously, all works perfectly, as I cannot test if the changeover was the problem because I need an 8/10 schedule.
This comment on another thread …
… came within a hair’s breadth of buying a 2nd 5kva MPII to eliminate the current inverter as the cause. 
Justified it further as the 2nd one is then the backup and have 8kw of power the rest of the time … till I sat myself down, slowly explaining to myself that having 2 inverters connected at the same time to the same DB, is not a “backup” with LS woes.
My cousin had 3 x 3kva’s, not only 3 times the power, but also 3 times the backup … till Eskom LS left him with one kinda crawling along, the bigger the inverter, the bigger the loads become. Learn from that I said.
Still want an older gen MLT as a backup.