Weird domain resolution behaviour with tailscale

Hello! I have a mt3000 and using tailscale with my vps as exitnode

now I have to say that on every device (android, windows…) is working great

When I configured tailscale on the router I have a very weird behaviour: only SOME domains get resolved, for instance google.* works, duckduckgo.* doesnt

I would not even know how to debug this and what/why is happening but only under the router this problem occures, I accepted all the advised subnets from the admin panel too

The domains I reported are only an example, for instance instagram, facebook all work while my university website doesnt, or this forum works too!
I know it sounds absurd but how can this be possible

If you manually set the dns of your computer to, can you resolve domain names normally?

You can use to check what dns server you are using. It is possible that tailscale’s dns server is causing some domain names to fail to resolve.

I changed to cloudflare (attached the dns leak results) and still nothing, some random domains are unreachable

and ping-ing these domains works