Virtualbox Debian repository requests 5.1.24, but it doesn't exist, prevents system update -> obsolete

[Fuquay]

When attempting to update my system (Ubuntu 17.04, 5.1.22), the Virtualbox Debian repository requests VirtualBox 5.1.24. However, it doesn't exist. *This error in the package definition prevents systems that use the repository from receiving ANY updates (without manual intervention) - not just VirtualBox.*

E: Failed to fetch http://download.virtualbox.org/virtualbox/debian/pool/contrib/v/virtualbox-5.1/virtualbox-5.1_5.1.24-117012~Ubuntu~zesty_amd64.deb  404  Not Found [IP: 88.221.50.105 80]

Note: A workaround that allows the system to be updated manually is to add the --ignore-missing flag to the apt or apt-get command.

[Fuquay]

This appears to have been fixed. VirtualBox 5.1.24 has been made available. (The URL is my report above no-longer reports a 404 Not Found status code, and I have been able to upgrade.)

[Fuquay]

I spoke too soon. On launching VirtualBox 5.1.24 for the first time I was prompted to install the extension pack, which resulted in "The network operation failed with the following error: During network request: Url not found on the server." It seems that there are still missing or inaccessible 5.1.24 resources for the moment.

Update: The extension pack at  http://download.virtualbox.org/virtualbox/5.1.24/Oracle_VM_VirtualBox_Extension_Pack-5.1.24.vbox-extpack downloads. However, at the following "Verifying VirtualBox Extension Pack..." an "Url not found on the server" is produced. So perhaps it just can't access filehashes to verify the integrity of the downloads? I can manually download the file hashes manually from:

 http://download.virtualbox.org/virtualbox/5.1.24/MD5SUMS  http://download.virtualbox.org/virtualbox/5.1.24/SHA256SUMS

I'm not sure what the problem is.

Update: I've been able to work around the problem by manually downloading and installing the extension pack (via Preferences > Extensions). The file I downloaded has md5 and sha256 hashes matching those in the above links.

[Fuquay]

The update process, including installation of updated extension pack and guest editions, worked fine on a separate machine a few hours later. I'm happy for this to be closed again.