Have you tried to just add your own entry? Manually works, or a script to populate it via a Jamf policy. But it's just inheriting what is auto discovered until you manually add an entry.

I do have similar issue. When user connected through VPN, we found Check Point-"CPiOSDefaultDNS" in Search Domain, and this causing user some other issues. But if I remove Check Point from Search Domain, it works like charm. Manually user cannot remove it, coz it requires Admin credentials. 

Does anyone have a script to remove this Checkpoint from Search Domain, so, user can remove it without Admin credentials.