Check out the following option:
It's on by default. Turning it off should help.
From the man page
Sets user home directory restriction. The off (or none) setting indicates that there is no home directory restriction for regular users. When this option is set to on (or homedir), each named account user's access is restricted to that user's own home directory or to the override directory, if one is specified by the ftpd.dir.override option.
Values: on, off, none, homedir
Effective: Upon FTP client reconnection
Persistence: Remains in effect across system reboots
Hope this helps.