Copied files may not have the expected file permissions. This issue is fixed in Security Update 2021-002 Catalina, iOS 14.5 and iPadOS 14.5, watchOS 7.4, tvOS 14.5, macOS Big Sur 11.3. The issue was addressed with improved permissions logic.
https://support.apple.com/en-us/HT212326
https://support.apple.com/en-us/HT212325
https://support.apple.com/en-us/HT212324