Wireless Networking – Wireguard VPN Not Working on FRITZ!Box After DNS Route Changes

I'm seeking assistance with troubleshooting a connectivity issue that arose after configuring Pi-Hole and DNS settings on my network. Here's a detailed overview of my setup and the problem:

Network Setup:

• Router: FRITZ!Box 6591 Cable
• Raspberry Pi Zero W connected via LAN, running Pi-Hole
• The Pi-Hole and network were functioning well until recent changes.

Initial Problem and Actions Taken:

• Identified that some devices (e.g. many Google devices) use hardcoded DNS servers
• To override this, I followed this tutorial for blocking Google DNS on FRITZ!Box
• Configured IPv4 route to redirect Google DNS (8.8.8.8 and 8.8.4.4) to the Pi-Hole's internal IP 192.168.178.61, with Subnet Mask 255.255.255.255.
• Initially, this seemed successful; pinging Google DNS timed out as expected.

Current Issue:

• The Wireguard VPN connection to the FRITZ!Box abruptly failed and hasn't been re-established.
• Multiple devices attempted, with no success.

VPN Configuration:

[Interface]
PrivateKey = [REDACTED FOR PRIVACY]
Address = 192.168.178.202/24
DNS = 192.168.178.1, fritz.box

[Peer]
PublicKey = [REDACTED FOR PRIVACY]
PresharedKey = [REDACTED FOR PRIVACY]
AllowedIPs = 192.168.178.0/24, 0.0.0.0/0
Endpoint = REDACTEDFORPRIVACY.myfritz.net:50974
PersistentKeepalive = 25

VPN Client Logs:

...
12:45:53 - peer(2MQH…8IT4) - UAPI: Updating endpoint
12:45:53 - Routine: receive incoming v4 - stopped
12:45:53 - Routine: receive incoming v6 - stopped
12:45:53 - UDP bind has been updated
12:45:53 - Routine: receive incoming v6 - started
12:45:53 - Routine: receive incoming v4 - started
12:45:58 - peer(2MQH…8IT4) - Handshake did not complete after 5 seconds, retrying (try 2)
12:45:58 - peer(2MQH…8IT4) - Sending handshake initiation
12:46:04 - peer(2MQH…8IT4) - Handshake did not complete after 5 seconds, retrying (try 2)
12:46:04 - peer(2MQH…8IT4) - Sending handshake initiation
12:46:09 - peer(2MQH…8IT4) - Handshake did not complete after 5 seconds, retrying (try 2)
12:46:09 - peer(2MQH…8IT4) - Sending handshake initiation
...

Additional Context

• The home internet appears functional as remote smart home control is possible.