Sometimes you don’t know the answer, but you see an error that is weird enough that it might be useful for googlers to have possible explanations. And that’s this case.
If you update kernel/initram disk for a repository, the way it’s implemented today will corrupt your files if the updated source file is larger than the old one. That’s the behavior of wget and we use that. It happens in real-world scenarios, we’ve seen this for Red Hat customers (kickstart was refreshed on CDN at least once, when using Katello plugin and changing OS variant from Server to Workstation and back it also happens).