Why does vsftpd fails with error "gnutls_record_recv: A record packet with illegal version was received"?

Issue

• vsftpd fails with the following error:

lftp -d -u test server1.example.com
Password: 
lftp test@server1.example.com:~> ls         
---- Connecting to server1.example.com (192.168.93.122) port 21
<--- 220-
<--- 220-               Welcome to ftp.example.com
<--- 220-
<--- 220-
<--- 220-
<--- 220-
<--- 220-
<--- 220-
<--- 220-
<--- 220-
<--- 220-
<--- 220-
<--- 220-
<--- 220-
<--- 220-
<--- 220-
<--- 220-
<--- 220 
---> FEAT
<--- 211-Features:
<---  AUTH SSL
<---  AUTH TLS
<---  EPRT
<---  EPSV
<---  MDTM
<---  PASV
<---  PBSZ
<---  PROT
<---  REST STREAM
<---  SIZE
<---  TVFS
<---  UTF8
<--- 211 End
---> AUTH TLS
<--- 234 Proceed with negotiation.
---> OPTS UTF8 ON
Certificate: C=US,ST=District of Columbia,L=Washington,O=US GAO,OU=ISTS,CN=vsftp,EMAIL=admins@example.com
 Issued by: C=US,ST=District of Columbia,L=Washington,O=US GAO,OU=ISTS,CN=vsftp,EMAIL=admins@example.com
WARNING: Certificate verification: Not trusted
WARNING: Certificate verification: The certificate's owner does not match hostname 'server1.example.com'

<--- 200 Always in UTF8 mode.
---> USER ygor
<--- 331 Please specify the password.
---> PASS XXXX
**** gnutls_record_recv: A record packet with illegal version was received.
---- Closing control socket
ls: Fatal error: gnutls_record_recv: A record packet with illegal version was received.