Some of our files can have / in their name (notably embedded files) which is causing weirdness when building a folder Zip archive. Per the specification it is not expected for files to have a / since it is the path separator:

4.4.17.1 The name of the file, with optional relative path. The path stored MUST NOT contain a drive or device letter, or a leading slash. All slashes MUST be forward slashes '/' as opposed to backwards slashes '' for compatibility with Amiga and UNIX file systems etc. If input came from standard input, there is no file name field.