process_usershare_file: stat of failed. Permission denied Samba
The cause is that Samba does not synchronize its users with the system.This solved the issue in my case, on Kubuntu 14.10:
sudo apt-get install libpam-smbpasssudo service samba restart
If you don't want to synchronize users with PAM, simply add a user to Samba's password database:
sudo smbpasswd -a <user>
After that, the user will be able to open shared folders on the Samba machine.
Your configuration file seems to be fine.
I reckon there might be a permission issue in your parent folder.
I suggest you check /home and /home/developer both have 755 rather than 750 permission.
Then check sudo -u nobody ls /home/developer/documents.
If ls is successful, the samba is likely to work as you expected as well