Recently we took over a client, whose entire network structure was just....abysmal. While doing an audit of the system, I discovered that my Domain Admin account had no access to the data drive on the file server.
I could get to the share without a problem, but could not access the drive through the server directly.
I took stock of who had access to what folders in the shares, and took control of the folder. Some hours later, after it had finished, I had full access to the security tab again, but I still could not access the drive normally.
Ultimately, the resolution was to the local server group "Users" with default access, as seen below.
Best practice is a thing for a reason. Never change the permissions on the drive - only on a folder.