PiHole Won't Respond to Requests on IPv4 but will on IPv6

[ClosedEyesSeeing]

Setup:

Running PiHole on a Debian 9 VM along side openvpn:

PRETTY_NAME="Debian GNU/Linux 9 (stretch)"
NAME="Debian GNU/Linux"
VERSION_ID="9"
VERSION="9 (stretch)"
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="Debian -- User Support"
BUG_REPORT_URL="https://bugs.debian.org/"

dhcpcd.conf:

slaac private
interface eth0
static ip_address=192.168.0.10/24
static routers=192.168.0.1
static domain_name_servers=8.8.8.8 8.8.4.4
interface eth1
static ip_address=192.168.0.11/24
static routers=192.168.0.1
static domain_name_servers=8.8.8.8 8.8.4.4

OpenVPN is using eth0 (192.168.0.10), PiHole eth1 (192.168.0.11) with IPV6 address set in setupVars.conf as fe80::fbd2:6f43:fb02:1a54

Testing client is Windows 10 with an ip on the same network: 192.168.0.72

Expected Behaviour:

Making DNS requests to 192.168.0.11 from Client respond with appropriate lookup.

Actual Behaviour:

DNS requests made by Client to 192.168.0.11 are not received by PiHole. However, when IPv6 is set to fe80::fbd2:6f43:fb02:1a54 PiHole receives the request and responds.

I've tested this using the following commands:

For IPv4: nslookup www.google.com 192.168.0.11
For IPv6: nslookup www.google.com fe80::fbd2:6f43:fb02:1a54

Responses:

IPV4:

DNS request timed out.
timeout was 2 seconds.
Server: UnKnown
Address: 192.168.0.11

DNS request timed out.
timeout was 2 seconds.

IPv6:

Server: openvpn
Address: fe80::fbd2:6f43:fb02:1a54

Non-authoritative answer:
Name: www.google.com
Addresses: 2607:f8b0:4004:80a::2004
172.217.7.164

I can ping 192.168.0.11 from the client. The client can access the pihole admin page and make configuration changes.

From the console, the pihole can ping the client, can ping the gateway, and can resolve dns queries locally.

Oddly, the pihole -d output says it cannot ping the gateway, but I can confirm that I can from the pihole server itself.

Debug Token:

gtqeiyo12k

My goal is to have PiHole be used only when configured as the DNS for clients. It is not being used for DHCP, I am letting the router (or openvpn when connecting from the outside) handle that.

Any help or guidance is greatly appreciated. Thanks so much for your time.

[ClosedEyesSeeing]

In the interim I've just spun up another deb VM and put pihole on there and all seems to be working perfect. I'll just stick with the two VM layout.

Thanks for anyone interested in helping!