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?