Pi-hole DHCP fails after about a day?

Expected Behaviour:

Pi-hole installed on Container Manager as per DrFrankensteins guide (Pi-hole in Container Manager on a Synology NAS). Using a BT Smart Hub 2 (no alternate choice as I'm a landline customer), the BT Hub's DHCP has to be disabled and Pi-hole's needs to be enabled.

Pi-hole should assign devices with IP addresses. I have even tried setting them all up statically by MAC address, also not working.

Actual Behaviour:

After about a day (the lease time from the BT Hub), the internet just stops working. It has been occasionally near impossible to even access my local network again so a few close calls where I thought I might have to factory reset my internet router. When the BT Hub's DHCP is re-enabled, internet access works again.

However if the BT Hub has DHCP on, Pi-hole stops filtering traffic, again after around 24 hours which is the lease time.

Two error messages I found:

Warning in dmasq core:
working around kernel bug: faulty source address scope for VRF slave eth0

Warning in dmasq core:
no address range available for DHCP request via eth0

I have the YAML here:

services:
pihole:
image: pihole/pihole:latest
container_name: pihole
cap_add:
- CAP_NET_RAW
- CAP_NET_BIND_SERVICE
- CAP_CHOWN
- NET_ADMIN
environment:
- PIHOLE_UID=1028 #CHANGE_TO_YOUR_UID
- PIHOLE_GID=100 #CHANGE_TO_YOUR_GID
- TZ=Europe/London #CHANGE_TO_YOUR_TZ
- WEBPASSWORD=
- DNSMASQ_LISTENING=local
- WEB_PORT=8000
- DNSMASQ_USER=pihole
- FTLCONF_LOCAL_IPV4=192.168.1.246
volumes:
- /volume1/docker/pihole/dnsmasq.d:/etc/dnsmasq.d
- /volume1/docker/pihole/pihole:/etc/pihole
network_mode: host
restart: unless-stopped

I think the Synology was losing its' DHCP assigned IP and thus Pihole was no longer accessible. I set the Synology's network interface to static rather than DHCP. It has worked for a day so far.

I should also add that I rang BT and they are sending a Smart Hub 3 which can set custom DNS.