About the system:
Multiplus II
MPPT RS
Raspberry Pi running Venus OS
VM3P75CT running as a grid meter connected via ethernet
I have had the ‘No grid meter: Warning’ 3 times in the last 2 months. I cannot pinpoint any anomalies that could easily explain it away. The warnings lasted: -1m (yes, negative), 15s and 7s. The first two occurred in quick succession about a minute apart and the last one a month later. Has anyone experienced this behaviour?
Anyone?
What sort of network connection does your Pi have, @Brian?
Wired
Without seeing logs from the time, it does sound an awful lot like you’ve experienced some temporary connection loss between your Pi and your VM-3P75CT.
There are, quite obviously, a large number of possible causes for a connection loss. If the entire network path between your Pi and energy meter is wired ethernet, and there are absolutely no link-layer issues that could be contributing to the drop-outs (i.e., a switch overheating, someone accidentally turning off a switch for a few moments, a dodgy cable, etc), then it may well be either a protocol-level issue (the VM-3P75CT uses Modbus over UDP, and UDP doesn’t have any inbuilt error correction — which is partly what led to the error I’d discussed elsewhere) or a software bug.
Again, without relevant logging, it’s difficult to say exactly.
The fact that it was for such a short period of time and so infrequently would mean that it’s probably not worth spending a lot of time chasing, IMHO 
It does sound as though the software recovered by itself and reconnected quickly. Is that right?
What OS version are you running?
Before 3.60 my issue involved the system not functioning got a while. 3.60 and later has some brief glitches which may be similar to what you’re seeing, but it recovers in a matter if seconds so it hasn’t been too concerning for me.