NextDNS set up on my Asus Merlin Router will suddenly stop resolving DNS queries

I'm using the native CLI tool to set it up, and suddenly, randomly, DNS queries will stop across all devices. The only way to solve is by rebooting the router.

The last thing to come up in the nextdns log command before there's suddenly no "Query"'s is the following;

Sep 29 18:50:38 nextdns[1074]: Connected [2a00:11c0:8:4::9]:443 (con=5ms tls=753ms, TCP, TLS13)
Sep 29 18:50:38 nextdns[1074]: Switching endpoint: https://dns.nextdns.io#209.250.226.191,2001:19f0:7401:85d3:5400:2ff:fec8:749f,37.252.230.153,2a00:11c0:8:4::9

Any ideas?