Went and fiddled with some of my Zappi settings yesterday which as the master device also controls and Eddi settings too.
Lowered my grid export margin from 100w to 50w and reduced the pause timer down to 30 secs.
This morning the Eddi has held onto generation coming from PV with the GivEnergy side outputting very low, 7w, in support of demand with the rest coming from PV generation.
It didn't change for over 5 minutes and had been like it for about 20 minutes prior looking at the Eddi chart info.
Swapped it back to 100w export margin and kept an eye on the myenegi app for updates, as expected the output from the battery and inverter icon on the Myenergi side gradually reduced until the Eddi was back awaiting surplus.
Checked the GivEnergy portal and once updated it then showed all spare PV going into the battery as expected.
I don't have a complex or long series of cable runs but it's clear the system doesn't like a smaller export margin in my case. I think it hung onto battery support post boiling the kettle.