I have a similiar grid metering setup, but I get updates every 5 seconds and I’ve never had oscillations longer than a minute or two, that visibly decreased. From reading other posts here, my gut feeling is that 10 seconds is just too slow for the control loop to be stable.
There is however a “RefreshTime” parameter in dbus under the grid meter, which seems to be in ms, which might help or not, see ESS control loop instable after upgrade to Venus v3.41 - #2 by Cubeteq