User Loses Membership Upon Login

We have found that the caching mechanism in Confluence 5.4.1 may be flawed (or any version of Confluence that comes with embedded Crowd 2.7.0) , in a way that users may randomly lose their group memberships once they login.

This is true even if the LDIF looks perfect, example:

1. Group confluence-users:

   dn: cn=confluence-users,ou=Groups,dc=example,dc=com
   objectClass: posixGroup
   objectClass: top
   cn: confluence-users
   memberUid: uid=foo,ou=Users,dc=example,dc=com
   

2. User foo:

   dn: uid=foo,ou=Users,dc=example,dc=com
   objectClass: posixAccount
   objectClass: top
   objectClass: inetOrgPerson
   gidNumber: 65534
   uid: foo
   givenName: foo
   sn: foo
   displayName: foo
   mail:foo@foo.foo
   cn: foo
   uidNumber: 64702
   userPassword: pass
   

3. Directory Configuration Summary:

       "ldap.basedn": "dc=example,dc=com"
       "ldap.group.dn": "ou=Groups"
       "ldap.group.filter": "(objectclass=posixGroup)"
       "ldap.group.name": "cn"
       "ldap.group.objectclass": "posixGroup"
       "ldap.group.usernames": "memberUid"
       "ldap.user.displayname": "displayName"
       "ldap.user.dn": "ou=Users"
       "ldap.user.email": "mail"
       "ldap.user.filter": "(objectclass=posixAccount)"
       "ldap.user.firstname": "givenName"
       "ldap.user.lastname": "sn"
       "ldap.user.objectclass": "posixAccount"
       "ldap.user.password": "userPassword"
       "ldap.user.username": "uid"
       "ldap.user.username.rdn": "uid"
       "ldap.usermembership.use": "false"
       "ldap.usermembership.use.for.groups": "false"
   

In the example above, foo will be the member of confluence-users after synchronization, but once foo logs into Confluence, he will no longer be a member of the said group.

The group only exists once in the entire LDAP directory, and so is the user

There are no synchronization errors in the logs whatsoever. The issue persists despite creating another directory with the same exact configuration in Confluence Administration >> User Directories, despite flushing all the caches, and a Confluence restart.

This issue is resolved by upgrading to Confluence 5.5 or greater, which uses a newer version of embedded Crowd