Report server is distributed stand alone. It runs under the account (Local System). While having a user with full permissions on a share configured in subscription there is no output written to the share. The user has share permissions plus NTFS permissions both full access. When I add that user to local admin group on the report server the report is written to the share. Any idea why we need any level of permissions on the report server?
I'd review the permissions on the share. Try creating a new shared directory with correct permissions for your user and then remove them from the local admins on the SSRS server and see if it works. I am thinking that the existing share has some permissions (directly or inherited) that are preventing your SSRS user from generating the output but the membership of the local admins group gives them sufficient for it to work