Bug#1061354: packages.debian.org: MIT mirror returns 503 error

Package: www.debian.org
Severity: important

Dear Maintainer,

packages.debian.org appears to likely have two physical hosts, one at MIT, and one
hosted via conova(?):

=========
packages.debian.org has address 128.31.0.51
packages.debian.org has address 195.192.210.132
packages.debian.org has IPv6 address 2603:400a:ffff:bb8::801f:33
packages.debian.org has IPv6 address 2a02:16a8:dc41:100::132

NetRange:       128.31.0.0 - 128.31.255.255
CIDR:           128.31.0.0/16
NetName:        MIT-RES

NetRange:       2603:4000:: - 2603:40FF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF
CIDR:           2603:4000::/24
NetName:        MIT-V6


inetnum:        195.192.208.0 - 195.192.215.255
netname:        AT-CONOVA-19960403

inet6num:       2a02:16a8:dc41:100::/56
netname:        CUS-DEBIAN
...
route6:         2a02:16a8::/32
descr:          conova communications GmbH IPv6 Route Object
=========

While the two conova-associated IPs seem to work fine, the MIT-associated hosts hang for 60 seconds before eventually returning a 503:

=========
$ time curl -I --resolve packages.debian.org:443:128.31.0.51 "https://packages.debian.org/sid/p7zip"
HTTP/2 503
...
real	1m4.353s

$ time curl -I --resolve packages.debian.org:443:[2a02:16a8:dc41:100::132] "https://packages.debian.org/sid/p7zip"
HTTP/2 200
...
real	0m0.519s

$ time curl -I --resolve packages.debian.org:443:[2603:400a:ffff:bb8::801f:33] "https://packages.debian.org/sid/p7zip"
HTTP/2 503
...
real	1m4.350s

$ time curl -I --resolve packages.debian.org:443:195.192.210.132 "https://packages.debian.org/sid/p7zip"
HTTP/2 200
...
real	0m0.523s
========

This also results in a web browser failing to load the page ~50% of the time (across launches).

I have confirmed this behavior from multiple ISPs, web browsers, and curl.