chocolatetrees I'm not sure how often the inverter (as Modbus master device) polls data from other Modbus devices: EM115 meter and battery(ies), but the squirt of data every five minutes to the portal is simply the contents of registers at that time. The portal is good but it just isn't of use to tell you what is happening across the piece at a single point in time. Even the 10s update on the app is the register contents at that time rather than the actual import/export measured by the EM115.
I think of it as looking out of the back window of a car on a journey: you felt the change of speed/direction, but it's only after you've passed the cat in the road or see the junction turned at, do you see what it was. And sometimes, the cat has disappeared, so you never know what caused the blip.