The UNL stratum 1 is getting 503 Service Temporarily Unavailable from the maxmind download site, which is cached by Cloudflare. Attempts to reproduce the issue show that a web page is returned saying that it is attributed to "DDoS protection by Cloudflare". This is using IPv6 which is the default on this system, and if I switch to IPv4 it works. I believe the only reason for the latter success is that it hasn't yet triggered the DDoS protection. I can also download OK over IPv6 from another machine at UNL. I don't know what triggered the original error, but all the many retries made the problem worse.
Change the download mechanism to not try more than 2 or 3 times per day. I think it would also be a good idea to prefer IPv4, although it looks like only wget can do that; curl can require ipv4, but apparently can't just prefer it.