Right, having had multiple LS in the mornings since the last error, with “no luck” … again, I opted to have the inverter replaced.
Simple logic: If the new unit goes up:
Option 1: And the error persistently stays away, then it was the relay all this time. How, no one knows.
Option 2: If the error persists, then as per (Error 8: Ground relay test failed on Victron Multiplus II GX - #62 by plonkster), then there is a blerrie persistent intermittent issue on the wiring of the house … but only during LS.
Thanks to @plonkster , for your participation.