backups: Cannot download or upload large archives

My FreedomBox generated an archive of 1.8 GB when I took a backup of all the applications. I wanted to test downloading this archive and uploading it into a virtual machine and see if the FreedomBox in the virtual machine looks behaves like my production FreedomBox.

Trying to download or upload the archive produces the same response from Apache, a 502 Proxy Error

I tried the same actions with a single application backup for MediaWiki which is 1.4 MB in size. Both downloading and uploading were successful.