Thanks for that @nickdb
My problem is solved for now with a workaround.
I created a Virtual Battery in NodeRed, fed it some values from my real BMS (voltage, current, watts, temperature, SoC) but omitted anything relating to historical charge/discharge data.
I then set the new Virtual battery to be the one tracking consumption in remote console. I retained the real BMS in DVCC to control the charge voltage, current, etc. Graphing is now working properly and the original problem has dissappeared. NodeRed was not too difficult to figure out by watching a couple of tutorials and googling a few examples. It’s reasonably intuitive. The worst bit was generating a short JavaScript code to edit some data to the expected format in a Function Node. I have prior programming experience in several languages but not in JavaScript. ChatGPT helped me generate that small piece of code and it was easy to understand.
Screenshot of my NodeRed flow (any further NodeRed discussion I will take to the suitable forum section 
) :
