Windows Server File Sharing Issues.

I have been banging my head one the wall at work for the last couple of weeks. I am having a problem with a file server showing different files to different users.

So say if User 1 goes to \\fileserver\data the user can see 5 files. If User 2 goes to same address they may see one or 2 files. Then User 3 can see all of the files.

We are running Server 2012 any help with this would be greatly appreciated.