Packer issue on Azure: `Could not connect to azure.archive.ubuntu.com:80`, connection timeout

Question

I've been building Ubuntu base images on Azure using Packer for the last year. Recently, I've been unable to complete a Packer build without errors.

The install script makes a bunch of apt-get install calls. Many of these succeed; however, at some (inconsistent) point, they start failing with the message:

Failed to fetch http://azure.archive.ubuntu.com/ubuntu/pool/universe/p/pigz/pigz_2.8-1_amd64.deb  Could not connect to azure.archive.ubuntu.com:80 (52.250.76.244), connection timed out

Obviously, the path depends upon what's being installed. In the case, it's failing when trying to install docker (sudo apt-get install -y docker-ce docker-ce-cli containerd.io). The other day, though, it was failing for the same reason when trying to run sudo apt-get install -y nfs-common earlier in the same script.

Does this look familiar to anyone? Any ideas for how to address this?