Exporting questionable statistics occurs when exporting Oracle databases in Linux. Error Handling

Environment: machine A and machine B are both Linux systems. However, machine B has insufficient space, so after the database service is stopped, you are ready to export data on machine.
Export Statement exp user/password @ Sid file = 0320.dmp
The error exporting questionable statistics. does not occur during the export process.
The character set is a problem.
Use a statement to view the character set of the database.
Select * From nls_database_parameters t where T. Parameter = 'nls _ characterset ';
Or
Selct * from V $ nls_parameters where parameter = 'nls _ characterset ';
The result is the same. Both devices A and B are zhs16gbk. Strange. Why not? After looking at the system character set of machine A, I found that it is in simplified Chinese. Will it be the problem?
Use it on machine A again
Export nls_lang = american_america.zhs16gbk
If you export data again, there will be no errors.
It turns out that the character set of the system is incorrect, rather than that of oracle.