You have one or more discover targets (Windows shares on a SAN or NAS device) that run for a period of time, then begin failing. The ScanDetail logs report the error: "Access denied."
This issue has appeared on SAN or NAS systems that present their data as Windows shares and have connectivity to Active Directory for file permissions. If the Active Directory connection is interrupted for any reason, Windows reports the "Access Denied" error when the discover server tries to access the files. You should check the connection with Active Directory to make sure that its connectivity is not interrupted.