TalkTalk hub overrides NextDNS Windows app

Before a recent upgrade from TalkTalk fast fibre to full fibre, I used to set DNS on the router as OpenDNS and used the NextDNS Windows app to override this for individual Windows computers. I didn't want to specify NextDNS in the router is it messes up a lot of the channels on my Roku TV box. That all worked fine.

I now have a new TalkTalk hub with full fibre. If I specify the OpenDNS settings in the router it overrides the NextDNS Windows app so that everything goes through OpenDNS (Cisco). Surely it shouldn't be able to do this as the device DNS takes precedence over the router DNS.