Custom login URL = get stuck at the login page

After using Custom login URL
when users try to login, they get stuck at the login page and need to manually change the url to wp-admin

Workaround: only if we use a Redirect user after login to some page it works

Looking at the log, i find 3 errors but not sure if it has anything to do with this:
E_NOTICE (8)
type Undefined variable: user_login
File wp-login.php
line 1305

E_NOTICE (8)
info Undefined variable: user_login
file wp-login.php
line 1379

type E_NOTICE (8)
info Undefined variable: error
file wp-login.php
line 1401