It sounds a bit like what I described here:
It almost works but not quite.
As a quick and admittedly dirty workaround, I set up a very simple Node-RED flow. I’d never used Node-RED before, so there are probably better approaches—but this one works:
This flow reads the limit that Venus OS calculated for me and passes it to the inverter via Modbus. It works like a charm. For my Kostal Inverter, it’s register 832.
So yeah—almost working.
Feature request for Victron: for Kostal inverters, Venus OS should allow specifying a Modbus port other than the default (502). That would make integration a lot easier.
And of course investigate why the limit never arrives at the inverter as in your case.
If anyone’s interested, I’m happy to share the full setup I used to get my Kostal Plenticore 10 G2 to limit AC feed-in.