Se os usuários não tiverem permissão de gravação no compartilhamento pai, eles não terão permissão de gravação nas subpastas. Você precisa dar permissão para alterar usuários no compartilhamento.
Postagem útil no blog aqui discutindo permissões de compartilhamento e NTFS: link
When you create a shared folder you apply share permissions and NTFS permissions (Read at a minimum) we’re clear on that. Next how do we determine the effective permissions on the shared folder? Simply put, you take the applied share + NTFS permissions and the most restrictive of the two get applied. For example: if you grant User-A Read share permissions and Full Control NTFS permissions, the most restrictive one will come out on top which is Read. Meaning that the user, or group of users, can’t create, delete or rename folders but just read and browse through them. The opposite is also true, when you grant User-A Read NTFS permissions and Full Control share permissions it’s still the Read permission that gets applied as being the most restrictive.