Nope, I don't know what this DAG error means. There is another post in this forum about DAG error but no answers.
My situation is a disaster, only one KD8003 out of 3 is working. One unit is bricked (with firmware 2.2.3) and it is offline whatever I have tried to do. Second KD8003 with 2.2.56 is online but cards and access codes don't work. This is my newest unit so perhaps therefore I was able to upgrade it from 2.0.8 via 2.2.3 to 2.2.56. I am now thinking that Hikvision has perhaps made some changes to the hardware so therefore my KD8003 units can't be upgraded to 2.2.56. I bought my KD8003 units in 2019-2020.
I contacted the reseller in Estonia yesterday but haven't received a reply yet. I'm planning to send my two KD8003 units to this reseller and ask them to downgreade the units.