DNS problems

[LazyLizard14 11]

I have set up AirVPN on my pfSense router with the help of the instructions I found here on this forum. Unfortunately I experience some DNS problems with the AirVPN DNS server 10.4.0.1. The AirVPN server is the first DNS (use VPN tunnel) and the other two OpenDNS server. Also the strict order option is set so se they are queried sequentially. I connect to german servers (UDP 443) but the problem not seems to be related to one certain server and may occur immediately after connecting to it or even after a day or two. Restarting the tunnel or the router itself fixes the problem, often needs a few tries.

Surprisingly it is only a few websites that are affected and cannot resolve properly. Those are for example (ironically) airvpn.org, windowscentral.com, pandawill.com just to mention a few.

If I omit AirVPN's DNS completely and only rely on the OpenDNS servers I not experience this issue at all and no DNS problems for weeks!

I attached some information and would appreciate any help on this.