User not getting unsubscribed from aweber lis

We have setup the plugin for Paypal and aweber integration. We have 2 types of users – FREE & PAID. The users are getting subscribed properly to both the lists as per our requirements. However the unsubscription is giving us a problem – when the user is migrated from PAID to FREE either manually or by Paypal IPN, it doesn’t show up the changes in aweber list. I tested out the plugin for 1 day access for X user. I noticed that everything works well, the user is migrated from PAID to FREE ( within the plugin) nicely, the log is generated for aweber too, but the user is not unsubscribed from the PAID list in aweber. I googled out a bit and saw the format of mail subject as :
REMOVE#lead@email.com#category#list1,list2

The one generated in the log is : REMOVE#USERX@MAIL.COM#s2Member#PAID_LIST_NAME

I’m unable to figure out as to why things are not working. I’m guessing the problem is somewhere with the category parameter ( #s2Member ). I’m unable to figure out what is this category in aweber. Where is it found? or I’ll have to tweak something in the plugin? Is it that important or it shouldn’t affect?

PS: I’ve set up the Email parser well, and registration with Paypal works good with addition of subscribers in the corresponding lists. Which means our server is sending the mails properly.

LOG ENTRY: Sat Aug 24th, 2013 @ precisely 12:22 pm UTC
PHP v5.5.1-2+debphp.org~precise+2 :: WordPress® v3.6 :: s2Member® v130816 :: s2Member® Pro v130816
Memory 3.28 MB :: Real Memory 3.50 MB :: Peak Memory 3.32 MB :: Real Peak Memory 3.50 MB
DOMAIN/wp-cron.php?doing_wp_cron=1377346947.4495389461517333984375
User-Agent: WordPress/3.6; http://DOMAIN
array (
  'function' => 'process_list_server_removals',
  'func_get_args' => 
  array (
    0 => 's2member_level1',
    1 => 1,
    2 => 'X',
    3 => false,
    4 => 'USERX@MAIL.COM',
    5 => 'X',
    6 => 'XY',
    7 => false,
    8 => true,
    9 => 21,
  ),
  'wp_mail_removal_method' => 'listUnsubscribe',
  'list_id' => 'rtcamp-testlist',
  'removal_bcc' => false,
  'wp_mail_removal_sbj' => 'REMOVE#USERX@MAIL.COM#s2Member#PAID_LIST_NAME',
  'wp_mail_removal_msg' => 'REMOVE',
  'wp_mail_removal_headers' => 'From: "TITLE" 
Content-Type: text/plain; charset=UTF-8',
  'wp_mail_removal_response' => true,
  'wp_mail_removal_success' => true,
)

Above is the log generated. I’ve edited some data for privacy purpose.
Also all the options under Automate Un-Subscribe settings are checked. and the last option in the dropdown titled “Also Process List Transitions Automatically?” is selected ( “Yes, even if NOT removed from previous list” )

Can someone shed a light on what I’m missing?