LDAP-based external user directory bug

When using LDAP-based external user directory, including group management, changing the Case (upper/lower/mixed) of a group name in LDAP results in incorrect behavior:

• "odd" logins (1st, 3rd, 5th, 7th, ...) result in a successful login (password check), but a "Not Authorized" result.
• "even" logins (2nd, 4th, 6th, ...) result in a successful login and proper authorization.

Two things about this:
1. Odd/Even login should not matter: why is the code behaving differently depending on whether it's the first/second login?
2. All comparisons between authorization criteria (e.g., group names) should occur by first "lowercaseing" both sides.