Still I am not able to login to the FTP server due to correct login details. I am getting this message “530 Login authentication failed”
Also, I have tried to reproduce this issue on my trail server but failed. It could be a has a chance of theme or plugin conflicts. You can disable all your plugins except User Frontend and switch to a default theme of WordPress like- Twenty Twelve, Twenty Thirteen, Twenty Fourteen and let me know the results.
The developer is still working to fix this bug. I have reproduced this issue but did not any inconsistency on my local server. Sometimes it is hard to find a bug but solution is easy. Hope I will fix this bug within tomorrow.