u/Few_Definition9354 — reddlx

I have been having Tailscale breaking on my iPhone 13 mini for a month. In short, it somehow messes with the internet connectivity. And turning off the Tailscale solves the problem. (But I can no longer access my Tailscale nodes) So I observed what's happening and I found out there are three ways it can break:

Case (1) Unusable at all:

iPhone WiFi Settings shows "No Internet Connection" in yellow text.
Tailnet lock is signed for this iPhone (So it's an approved device.)
Tailscale ACL is not there.
Pinging 1.1.1.1 from aShell app fails (Request timeout for icmp_seq).
nslookup google.com returns: "connection timed out; no server reached"
Only iPhone is affected. I have several clients such as Mac and Android and they also use Tailscale DNS. They are both unaffected.
The issue happens constantly but also goes away some time. Overall it's utterly unpredictable. 80% of the time, the issue is there.

Case (2) Somewhat usable:

Tailnet lock is signed for this iPhone (So it's an approved device.)
Tailscale ACL is not there.
Pinging 1.1.1.1 from aShell app succeeds().
nslookup google.com returns: "connection timed out; no server reached"
Can still visit/refresh websites with safari (maybe dns in cache?).
Only iPhone is affected. I have several clients such as Mac and Android and they also use Tailscale DNS. They are both unaffected.
The issue happens constantly but also goes away some time. Overall it's utterly unpredictable. 80% of the time, the issue is there.

Case (3) I don't understand why this happens:

Tailnet lock is signed for this iPhone (So it's an approved device.)
Tailscale ACL is not there.
Pinging 1.1.1.1 from aShell app succeeds().
nslookup google.com returns: 100.100.100.100 and loses it in another trial shortly after a few seconds -> Case (2)
Can visit websites with safari.
Only iPhone is affected. I have several clients such as Mac and Android and they also use Tailscale DNS. They are both unaffected.
The issue happens constantly but also goes away some time. Overall it's utterly unpredictable. 80% of the time, the issue is there.

So far I've tried but didn't solve the issue:

Turning off and on the VPN toggle in the first screen of Tailscale. (Some people seem to claim this fixes the issue temporarily. But in my case, it doesn't. )
Turning “VPN on demand” off since I was using both WiFi & cellular to "Always"
setting "Configure DNS to "Manual" in iPhone WiFi Settings and adding commonly known public DNS such as cloudflare's ipv4&ipv6 (Previously, it was set to "Automatic")
Uninstall & Re-install the Tailscale app
Turning off "Use Tailscale DNS Settings" (it doesn't really help though since I heavily rely on Tailscale DNS anyway. )
Turning off "Override DNS servers" on Tailscale Web UI.
Changing "Global nameservers" from AdGuard public ones to Cloudflare ones on Tailscale Web UI.

Is my iPhone broken? Should I reinstall the iOS?