I have seen this error prior, here's what we discovered in the past. also based on the log below it looks like this is prior to provisioning, therefore I would check the name in the DHCP for Option #15.
Soap Error 23
If Prior to provisioning -> validate Option 15 using the right CN.
If after provisioning --> Kerberos.
Let me know..
My understanding of DNS option 15 is more for the vPro client when it tries to contact provisionserver.<domainname> for provisioning. Since we are using RCT, the provisionserver.<domainname> handshaking is not needed any more. As now, we can see client.<domainname> properly. It also resolved the right IP. But for some reasons, SCS cannot connect to client based on IP as shown in the log. Is this still related to option 15?
I will try to get the entire log to show the actual message