Sharing Files on a P2P network

I currently have a user on a small P2P the network of about 5 that whenever they make changes to a shred file it removes permissions on that file so ohter users in the network no longer have access. I have checked and double checked Security and Permissions on the shared folder and went as far as giving “Everyone” access to the folder but the same thing keeps happening. I have tried turning on and off Inherit permsiions.
Any ideas about what I am not looking at?