Vsftpd configures multiple users, and the last one cannot log in

I set up a vsftpd in centos6 to set up a virtual user list. The last virtual user is always unable to log in.

that is, to create three accounts, only two can log in, and only the first three can log in when creating four. Have you ever encountered this problem

Mar.10,2021
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-7b5a54-155a4.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-7b5a54-155a4.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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