I have a SQL cluster backup with two instances. The first instace make backup with no erros, but other instance give some connection errors.

- Allow remote connections is enable;

- SQL Server 2012;

- Windows authentication;

- I had open all ports of firewall and the issue persists;

Log below:

2017-11-07 15:02:54 avsql Info <5008>: Logging to K:\Program Files\Backup Agents for Cluster Groups\SQL Server (TERCEIROS)\var\DMZ-1510074185415-3006-SQL.log

2017-11-07 15:02:54 avsql Info <6673>: CTL listening on port 65317

2017-11-07 15:02:54 avsql Info <10684>: Setting ctl message version to 3 (from 1)

2017-11-07 15:02:54 avsql Info <16136>: Setting ctl max message size to 268435456

2017-11-07 15:02:54 avsql Info <7838>: - Adding user exclude "*/tempdb"

2017-11-07 15:02:54 avsql Info <0000>: Adding SQL Database '*/tempdb' to EXCLUDE list

2017-11-07 15:02:54 avsql Info <7062>: Targets count 4

2017-11-07 15:02:54 avsql Info <7063>: target[0] = 'TERCEIROS\TERCEIROS/dbCitsmart'

2017-11-07 15:02:54 avsql Info <7063>: target[1] = 'TERCEIROS\TERCEIROS/dbCitsmart2'

2017-11-07 15:02:54 avsql Info <7063>: target[2] = 'TERCEIROS\TERCEIROS/dbCitsmart3'

2017-11-07 15:02:54 avsql Info <7063>: target[3] = 'TERCEIROS\TERCEIROS/dbDeepSecurity'

2017-11-07 15:02:54 avsql Info <7065>: Working on target 'TERCEIROS\TERCEIROS/dbDeepSecurity/f-0'

2017-11-07 15:02:54 avsql Info <14293>: Creating a database task for 'TERCEIROS\TERCEIROS/dbDeepSecurity/f-0' (hcount 166)

2017-11-07 15:04:35 avsql Error <9072>: sqlconnectimpl_smo::connect Microsoft.SqlServer.Management.Common.ConnectionFailureException: Failed to connect to server 10.0.253.18. ---> System.Data.SqlClient.SqlException: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
  at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)
  at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning()
  at System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean integratedSecurity)
  at System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, TimeoutTimer timeout, SqlConnection owningObject)
  at System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo serverInfo, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, TimeoutTimer timeout)
  at System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, TimeoutTimer timeout, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance)
  at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance)
  at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection)
  at System.Data.ProviderBase.DbConnectionFactory.CreateNonPooledConnection(DbConnection owningConnection, DbConnectionPoolGroup poolGroup)
  at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection)
  at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
  at System.Data.SqlClient.SqlConnection.Open()
  at Microsoft.SqlServer.Management.Common.ConnectionManager.InternalConnect(WindowsIdentity impersonatedIdentity)
  at Microsoft.SqlServer.Management.Common.ConnectionManager.Connect()
  --- End of inner exception stack trace ---
  at Microsoft.SqlServer.Management.Common.ConnectionManager.Connect()
  at SMOWrap.SMO_Connect(SMOWrap* , UInt16* server, UInt16* login, UInt16* password, Int32 timeout)
2017-11-07 15:04:35 avsql Warning <16255>: Connecting to SQL Server '10.0.253.18' failed, attempting to establish a connection to 'TERCEIROS\TERCEIROS' instead.

Any ideas?