PFLogInViewController error - unable to login to Facebook after exiting Parse mode

I am using PFLogInViewController for facebook login which works successfully the first time -

- (void)logInViewController:(PFLogInViewController *)controller
           didLogInUser:(PFUser *)user {
if([PFFacebookUtils isLinkedWithUser:user]){
    FBRequest *request = [FBRequest requestForMe];
    [request startWithCompletionHandler:^(FBRequestConnection *connection, id result, NSError *error) {
        NSDictionary *userData = (NSDictionary *)result;

        NSString *facebookID = userData[@"id"];
        NSString *name = userData[@"name"];
        NSString *location = userData[@"location"][@"name"];
        NSString *gender = userData[@"gender"];
        NSString *birthday = userData[@"birthday"];
        NSString *relationship = userData[@"relationship_status"];

        [user setObject:userData[@"id"] forKey:@"fbId"];
        [user setObject:userData[@"name"] forKey:@"name"];
        [user setObject:userData[@"email"] forKey:@"email"];
        [user saveInBackground];
        NSURL *pictureURL = [NSURL URLWithString:[NSString stringWithFormat:@"https://graph.facebook.com/%@/picture?type=large&return_ssl_resources=1", facebookID]];
        NSURLRequest *urlRequest = [NSURLRequest requestWithURL:pictureURL];

        // Run network request asynchronously
        [NSURLConnection sendAsynchronousRequest:urlRequest
                                           queue:[NSOperationQueue mainQueue]
                               completionHandler:
         ^(NSURLResponse *response, NSData *data, NSError *connectionError) {
             if (connectionError == nil && data != nil) {
                 // Set the image in the header imageView
                 PFFile *profileImage=[PFFile fileWithData:data];
                 [user setObject:profileImage forKey:@"profileImage"];
                 [user saveInBackground];
             }
         }];

    }];
}

[self dismissViewControllerAnimated:YES completion:nil];

      

        
        
        
      

    

}

If I then call [PFUser logOut] and reopen PFLogInViewController, when I touch the facebook icon to login again, the facebook spinner spins endlessly and I get the error "Attempting to change objectId to one already known to OfflineStore."

How do I log out of the current user and then log back in with the PFLogInViewController?