Overview:
Using the non-standard ASCII character ł in the Key Message content results in an error in the Offline Veeva CRM Application: Incorrect Packaging Structure. This occurs once the Key Message is downloaded.
Answer:
Replacing this character to a normal ASCII character resolves the error.
This behavior is working as designed, this character must not be used in the compressed (.zip) content.
Related Documentation:
CRM Help Documentation: Content Packaging