Quote Originally Posted by djtrillian View Post
It is some kind of Zen Cart issue, perhaps dealing with GZip compression even though it is switched off in the admin area.
Um, no.

Zen Cart never deletes anything from the /download/ folder. Unless you've added code to do that.

When using download-by-redirect, the temporary-user-specific-download-symlink is placed in the /pub/ folder so they can do their download. That symlink is later removed as cleanup. But it never touches the original file in the /download/ folder, and thus never affects future downloads.