An extract of the system log, if that can help:
Tue Dec 14 11:24:26 2021 daemon.notice netifd: Interface 'wan6' is now up
Tue Dec 14 11:24:26 2021 daemon.info dnsmasq[3377]: reading /tmp/resolv.conf.auto
Tue Dec 14 11:24:26 2021 daemon.info dnsmasq[3377]: using local addresses only for domain test
Tue Dec 14 11:24:26 2021 daemon.info dnsmasq[3377]: using local addresses only for domain onion
Tue Dec 14 11:24:26 2021 daemon.info dnsmasq[3377]: using local addresses only for domain localhost
Tue Dec 14 11:24:26 2021 daemon.info dnsmasq[3377]: using local addresses only for domain local
Tue Dec 14 11:24:26 2021 daemon.info dnsmasq[3377]: using local addresses only for domain invalid
Tue Dec 14 11:24:26 2021 daemon.info dnsmasq[3377]: using local addresses only for domain bind
Tue Dec 14 11:24:26 2021 daemon.info dnsmasq[3377]: using local addresses only for domain lan
Tue Dec 14 11:24:26 2021 daemon.info dnsmasq[3377]: using nameserver 2a0e:404:0:a::1#53
Tue Dec 14 11:24:26 2021 daemon.info dnsmasq[3377]: using nameserver 2a0e:404:0:a::2#53
Tue Dec 14 11:24:26 2021 daemon.notice netifd: Interface 'wan6_4' is setting up now
Tue Dec 14 11:24:26 2021 daemon.notice netifd: wan6 (8949): Command failed: Unknown error
Tue Dec 14 11:24:26 2021 daemon.notice netifd: wan6_4 (23196): Skipped invalid value for option ipv6prefix
Tue Dec 14 11:24:26 2021 daemon.notice netifd: wan6_4 (23196): Skipped invalid value for option prefix6len
Tue Dec 14 11:24:26 2021 daemon.notice netifd: wan6_4 (23196): Skipped invalid value for option ipv4prefix
Tue Dec 14 11:24:26 2021 daemon.notice netifd: wan6_4 (23196): Skipping invalid or incomplete rule: type=map-t,ipv6prefix=,prefix6len=,ipv4prefix=,prefix4len=32,dmr=
Tue Dec 14 11:24:26 2021 daemon.notice netifd: Interface 'wan6_4' is now down