There is a missing > on line 1687 of auth/ldap/auth.php, introduced in https://tracker.moodle.org/browse/MDL-42834 I did a quick check of the other changes in this commit but just this one line is missing the character

+ redirect($CFG-wwwroot.'/login/index.php?authldap_skipntlmsso=1');

I've added that > to my local files and it works correctly again

The result is that when NTLM login fails (due to unsupported browser within NTLM subnet) it attempts to redirect to the manual login page (/login/index.php?authldap_skipntlmsso=1) but now fails as the redirect link is generated incorrectly with extra characters (/login/1/login/index.php?authldap_skipntlmsso=1)

 Rob