Gluetun not always working and maybe DNS leaking

[LorenzoZappa]

I have installed Gluetun on my Ubuntu server, which is using hotspot shield vpn.
I am currently connecting to that server using Tailscale and on the same server I am running pi-hole as DNS filter. In short I have tailscale and pi-hole configured on my server so that any client logged into the same tailscale network always uses my server IP for DNS requests.
On the same server I have installed Gluetun with docker, to use the vpn with other containers. I think that gluetun might try to resolve the dns request using my pi-hole dns server, due to tailscale redirecting all dns requests to it.
Today gluetun stopped working completely, here is the docker log

2025-04-14T18:12:52+02:00 INFO [vpn] starting
2025-04-14T18:12:52+02:00 INFO [firewall] allowing VPN connection...
2025-04-14T18:12:52+02:00 INFO [openvpn] DEPRECATED OPTION: --cipher set to 'AES-128-CBC' but missing in --data-ciphers (AES-256-GCM:AES-128-GCM:CHACHA20-POLY1305). OpenVPN ignores --cipher for cipher negotiations. 
2025-04-14T18:12:52+02:00 INFO [openvpn] OpenVPN 2.6.11 x86_64-alpine-linux-musl [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [MH/PKTINFO] [AEAD]
2025-04-14T18:12:52+02:00 INFO [openvpn] library versions: OpenSSL 3.3.2 3 Sep 2024, LZO 2.10
2025-04-14T18:12:52+02:00 WARN [openvpn] --ping should normally be used with --ping-restart or --ping-exit
2025-04-14T18:12:52+02:00 INFO [openvpn] TCP/UDP: Preserving recently used remote address: [AF_INET]103.219.168.75:8041
2025-04-14T18:12:52+02:00 INFO [openvpn] UDPv4 link local: (not bound)
2025-04-14T18:12:52+02:00 INFO [openvpn] UDPv4 link remote: [AF_INET]103.219.168.75:8041
2025-04-14T18:12:52+02:00 INFO [openvpn] [lawyerforum.us] Peer Connection Initiated with [AF_INET]103.219.168.75:8041
2025-04-14T18:12:53+02:00 INFO [openvpn] TUN/TAP device tun0 opened
2025-04-14T18:12:53+02:00 INFO [openvpn] /sbin/ip link set dev tun0 up mtu 1500
2025-04-14T18:12:53+02:00 INFO [openvpn] /sbin/ip link set dev tun0 up
2025-04-14T18:12:53+02:00 INFO [openvpn] /sbin/ip addr add dev tun0 10.254.128.15/17
2025-04-14T18:12:57+02:00 WARN [dns] dialing tls server for request IN A cloudflare.com.: dial tcp 1.0.0.1:853: i/o timeout
2025-04-14T18:12:58+02:00 ERROR [openvpn] OpenVPN tried to add an IP route which already exists (RTNETLINK answers: File exists)
2025-04-14T18:12:58+02:00 WARN [openvpn] Previous error details: Linux route add command failed: external program exited with error status: 2
2025-04-14T18:12:58+02:00 ERROR [openvpn] Linux route add command failed
2025-04-14T18:12:58+02:00 INFO [openvpn] UID set to nonrootuser
2025-04-14T18:12:58+02:00 INFO [openvpn] Initialization Sequence Completed
2025-04-14T18:12:59+02:00 WARN [dns] dialing tls server for request IN A cloudflare.com.: dial tcp 1.0.0.1:853: i/o timeout
2025-04-14T18:13:01+02:00 WARN [dns] dialing tls server for request IN A tracker.internetwarriors.net.: dial tcp 1.1.1.1:853: i/o timeout
2025-04-14T18:13:01+02:00 WARN [dns] dialing tls server for request IN AAAA tracker.XXXXX.net.: dial tcp 1.1.1.1:853: i/o timeout
2025-04-14T18:13:03+02:00 WARN [dns] dialing tls server for request IN A ipinfo.io.: dial tcp 1.1.1.1:853: i/o timeout
2025-04-14T18:13:03+02:00 WARN [dns] dialing tls server for request IN AAAA ipinfo.io.: dial tcp 1.0.0.1:853: i/o timeout
2025-04-14T18:13:03+02:00 WARN [dns] dialing tls server for request IN AAAA tracker.XXXXX.net.: dial tcp 1.1.1.1:853: i/o timeout
2025-04-14T18:13:03+02:00 WARN [dns] dialing tls server for request IN A tracker.XXXXX.net.: dial tcp 1.0.0.1:853: i/o timeout
2025-04-14T18:13:03+02:00 WARN [dns] dialing tls server for request IN A cloudflare.com.: dial tcp 1.0.0.1:853: i/o timeout
2025-04-14T18:13:06+02:00 WARN [dns] dialing tls server for request IN AAAA tracker.XXXXX.gr.: dial tcp 1.0.0.1:853: i/o timeout
2025-04-14T18:13:06+02:00 WARN [dns] dialing tls server for request IN A tracker.XXXXX.net.: dial tcp 1.1.1.1:853: i/o timeout
2025-04-14T18:13:06+02:00 WARN [dns] dialing tls server for request IN AAAA tracker.XXXXX.net.: dial tcp 1.0.0.1:853: i/o timeout
2025-04-14T18:13:06+02:00 WARN [dns] dialing tls server for request IN A tracker.XXXXX.gr.: dial tcp 1.0.0.1:853: i/o timeout
2025-04-14T18:13:08+02:00 WARN [dns] dialing tls server for request IN AAAA ipinfo.io.: dial tcp 1.1.1.1:853: i/o timeout
2025-04-14T18:13:08+02:00 WARN [dns] dialing tls server for request IN A ipinfo.io.: dial tcp 1.1.1.1:853: i/o timeout
2025-04-14T18:13:08+02:00 WARN [dns] dialing tls server for request IN AAAA tracker.XXXXX.gr.: dial tcp 1.0.0.1:853: i/o timeout
2025-04-14T18:13:08+02:00 WARN [dns] dialing tls server for request IN A tracker.XXXXX.gr.: dial tcp 1.1.1.1:853: i/o timeout
2025-04-14T18:13:08+02:00 WARN [dns] dialing tls server for request IN A cloudflare.com.: dial tcp 1.0.0.1:853: i/o timeout
2025-04-14T18:13:09+02:00 WARN [dns] dialing tls server for request IN A cloudflare.com.: dial tcp 1.1.1.1:853: i/o timeout

(where the XXXX has been edited out)

Looking at this it seems to me that not only Gluetun is not working but it is leaking my dns, so even if it works it would still be an issue. Is it leaking dns requests?

Here is my docker-compose.yml

services:
  gluetun:
    container_name: gluetun
    image: qmcgaw/gluetun:latest
    restart: unless-stopped
    cap_add:
      - NET_ADMIN
    devices:
      - /dev/net/tun:/dev/net/tun
    volumes:
      - ./vpn.ovpn:/gluetun/custom.conf:ro
    environment:
      - VPN_SERVICE_PROVIDER=custom
      - VPN_TYPE=openvpn
      - OPENVPN_CUSTOM_CONFIG=/gluetun/custom.conf
      - OPENVPN_USER=XXXXXXX
      - OPENVPN_PASSWORD=XXXXXXX
      - TZ=Europe/Rome
    ports:
      - 9696:9696 
      - 8989:8989 #
      - 8580:8580 #
      - 6881:6881 #
      - 6881:6881/udp
      - 7878:7878 #