Make sure this line in web.config
<add name="udpTransportCustom" type="Microsoft.ServiceModel.Samples.UdpTransportElement, EPiServer.Framework" />
is updated to
<add name="udpTransportCustom" type="Microsoft.ServiceModel.Samples.UdpTransportElement, EPiServer.Framework.AspNet" />
Should this just be in the DXC envionment?
No, the upgrade should work just fine - and this is not DXC-specific. You might have a web.config transformation which changes it back to the wrong value.
I've checked this in the commerce manager application and it's correct to what you've said it should be and there's no config transforms that would affect it. We have seen the Pass portal sometimes not be able to copy over locked files and it's the first deployment of the new code so I'll try another deployment.
I'm getting an error around the thumbnail manager after doing an upgrade a few days ago only on the DXC. Has anyone come across it?