View the information about the error message numbered 25 in Symantec documentation. The problem occurs because the program cannot connect to the socket.
Go to the /usr/openv/netbackup/bin directory to locate the bprd process startup failure, and find that the bprd.d folder does not exist but a file with the same name exists. The bprd process needs to create files in the folder, so it cannot start up because the folder does not exist.
Delete the bprd.d file, and create a folder with the same name. Then the bprd process startup succeeds. Start a backup task, and no error is reported.