Wireguard stopped working.

[samyamer]

In raising this issue I confirm the following:

• I have read the documentation
• I have read and understood the contributors guide.

Have you searched for similar issues and solutions?

• Yes, but I cannot find anything quite like this

Has your install failed?

• No, successful install

System Information

Hardware

• Pi Zero

uname -a

 Linux raspberrypi 6.1.21+ #1642 Mon Apr  3 17:19:14 BST 2023 armv6l GNU/Linux

Output of cat /etc/os-release

  PRETTY_NAME="Raspbian GNU/Linux 11 (bullseye)"
NAME="Raspbian GNU/Linux"
VERSION_ID="11"
VERSION="11 (bullseye)"
VERSION_CODENAME=bullseye
ID=raspbian
ID_LIKE=debian
HOME_URL="http://www.raspbian.org/"
SUPPORT_URL="http://www.raspbian.org/RaspbianForums"
BUG_REPORT_URL="http://www.raspbian.org/RaspbianBugs"

Issue

The connection between my phone (4G) and the pi is very finicky. It works 1 time out of 10. When it's not working, the log shows a failed handshake. However, the tcpdump ALWAYS shows that there is communication between the phone and the pi (even when the handshake is failing).

(I have followed the troubleshooting guide and I couldn't find anything out of order.

pivpn -d output:

Generating Debug Output
::::		PiVPN debug		 ::::
=============================================
::::		Latest commit		 ::::
Branch: master
Commit: 4032a55c80f25b51419180eda93f44d579ab79e9
Author: 4s3ti
Date: Wed Mar 29 14:54:19 2023 +0200
Summary: docs(issues): Remove old markdown template
=============================================
::::	    Installation settings    	 ::::
PLAT=Raspbian
OSCN=bullseye
USING_UFW=0
pivpnforceipv6route=1
IPv4dev=wlan0
dhcpReserv=1
IPv4addr=192.168.1.53/24
IPv4gw=192.168.1.1
install_user=samyamer
install_home=/home/samyamer
VPN=wireguard
pivpnPORT=51820
pivpnDNS1=9.9.9.9
pivpnDNS2=149.112.112.112
pivpnHOST=REDACTED
INPUT_CHAIN_EDITED=0
FORWARD_CHAIN_EDITED=0
INPUT_CHAIN_EDITEDv6=
FORWARD_CHAIN_EDITEDv6=
pivpnPROTO=udp
pivpnMTU=1420
pivpnDEV=wg0
pivpnNET=10.83.143.0
subnetClass=24
pivpnenableipv6=0
ALLOWED_IPS="0.0.0.0/0, ::0/0"
UNATTUPG=1
INSTALLED_PACKAGES=(unattended-upgrades)
=============================================
::::  Server configuration shown below   ::::
[Interface]
PrivateKey = server_priv
Address = 10.83.143.1/24
MTU = 1420
ListenPort = 51820
begin test
[Peer]
PublicKey = test_pub
PresharedKey = test_psk
AllowedIPs = 10.83.143.2/32
 end test 
=============================================
::::  Client configuration shown below   ::::
[Interface]
PrivateKey = test_priv
Address = 10.83.143.2/24
DNS = 9.9.9.9, 149.112.112.112

[Peer]
PublicKey = server_pub
PresharedKey = test_psk
Endpoint = REDACTED:51820
AllowedIPs = 0.0.0.0/0, ::0/0
=============================================
:::: 	Recursive list of files in	 ::::
::::	/etc/wireguard shown below	 ::::
/etc/wireguard:
configs
keys
wg0.conf

/etc/wireguard/configs:
clients.txt
test.conf

/etc/wireguard/keys:
server_priv
server_pub
test_priv
test_psk
test_pub
=============================================
::::		Self check		 ::::
:: [OK] IP forwarding is enabled
:: [OK] Iptables MASQUERADE rule set
:: [OK] WireGuard is running
:: [OK] WireGuard is enabled 
(it will automatically start on reboot)
:: [OK] WireGuard is listening on port 51820/udp
=============================================
:::: Having trouble connecting? Take a look at the FAQ:
:::: https://docs.pivpn.io/faq
=============================================
:::: WARNING: This script should have automatically masked sensitive       ::::
:::: information, however, still make sure that PrivateKey, PublicKey      ::::
:::: and PresharedKey are masked before reporting an issue. An example key ::::
:::: that you should NOT see in this log looks like this:                  ::::
:::: YIAoJVsdIeyvXfGGDDadHh6AxsMRymZTnnzZoAb9cxRe                          ::::
=============================================
::::		Debug complete		 ::::
::: 
::: Debug output completed above.
::: Copy saved to /tmp/debug.log
::: 

I have checked my DDNS IP address (and that it updates when the address changes) and port forwarding (which are also confirmed by the fact that the connection works some of the time and the tcpdump shows conversation)

TL,DR: Handshake failing most of the time when testing on 4g. tcpdump shows conversation even when handshake fails.

Thank you!

(P.S.: I couldn't find the template (404) so I did my best to follow it)