I have two users. One that is actually a real user on the machine. And one that have no ubuntu account. Both users are set to use "fake root" with the same settings. The one with the real account have no trouble to log in but the other user gets a 530 login authentication error. like this:
Response: 220---------- Welcome to Pure-FTPd [privsep] [TLS] ----------
Response: 220-You are user number 1 of 50 allowed.
Response: 220-Local time is now 19:35. Server port: 21.
Response: 220-This is a private system - No anonymous login
Response: 220-IPv6 connections are also welcome on this server.
Response: 220 You will be disconnected after 15 minutes of inactivity.
Command: USER test
Response: 331 User test OK. Password required
Command: PASS ****
Response: 530 Login authentication failed