Embeded objects gets doubled [see description for the whole scenario]

If you have the database structure as:
'Group' Collection has 'tables' (ReferenceMany targetDocument="Documents\Table") and 'chairs' (ReferenceMany targetDocument="Documents\Chair").
'Table' Collection has 'glasses' (EmbedMany targetDocument="Documents\Glass") and a name as (@String).
'Chair' Collection has a name as (@String) and tablenames as (@Hash).
'Glass' Collection has name as (@String).

First, I simply add a glass to table and add that table to group. And create a chair and add it to group also.
$dm = $this->doctrine->getDM();
$group = new Group();
$table = new Table();
$chair = new Chair();
$glass = new Glass();

$group->tables[] = $table;
$group->chairs[] = $chair;
$table->glasses[] = $glass;

$dm->persist($group);
$dm->flush();
*At this point the tablenames in 'Chair' collection is not entered.

Now I call a function, which adds a new chair;
function addChair()
{
$dm = $this->doctrine->getDM();
$chair = new Chair();
$group = $dm->createQuery('Documents\Group')
->where('name','group')
->getSingleResult();
foreach($group->tables as $table)

$group->chairs[] = $chair;
$dm->persist($chair);
$dm->flush();
}

and as mentioned I traverse on tables to get table names and add those name in a new 'Chair' Collection's tablenames (@Hash).

Now in Db I have:
a group with two chairs and a table (both Referenced).
two chairs (one with an array of "tablenames" and one doesn't have "tablenames"),
a table with "TWO" embedded glasses <<--this is very strange I never added another glass to table!!!!

Note: As I call "addChair()" one more time the glasses in table get multiplied by two!!!
Please fix this asap.
Thanks
Regards
Ahsan