Sometimes, mostly after updating vsftpd ignores to make good connections.
The logfile often looks like this:

[14:21:47] 220 Welcome to BLA FTP service.
[14:21:47] USER foo.com
[14:21:47] 331 Please specify the password.
[14:21:47] PASS
[14:21:47] 230 Login successful.
[14:21:47] SYST
[14:21:47] 500 OOPS: cap_set_proc
[14:21:47] FEAT
[14:21:47] 215 UNIX Type: L8

There’s a simple solution for that just type in: modprobe capability


Hope that’s help!