A bit of an update with some data gathered:
@robmeerwijk there seems to be some similarity with the phenomenon you have observed that the grid meter data flow is lost for a few minutes at a time but recovers automatically.
The node red monitoring I have set up emails me if there has been no data received for 5 minutes, and since 2pm there have been several periods where the alert has been triggered: 14:13, 15:05, 15:27 and 17:20 so there is no discernable pattern it has been very dark and rainy here (Northern UK) so there has been little PV and the battery is in sustain mode having not been charged overnight last night as the system was in Passthrough.
I also looked at the VRM data from last night and it looks like the system entered passthrough mode when the scheduled charge began, there was a brief jump in DC Bus current and thus battery voltage at 01:30 (scheduled time for charge) but then stopped after 1 data point was collected:
Comparing the Grid input power over the last 7 days the charging has worked fine until last night:
The cursor is on the brief rise around 0130 last night but for the previous 6 nights the charge has happened normally.
Still no real idea what is happening but at least in this case there is an obvious trigger event, even if it is not consistent !