eh...even though this post like quite late.....
i noticed the bump too when i accompanied my friend to buy his
Slim, but after i asked the shopkeeper for another set, the 2nd set
also had the same bump. So i think its natural defect.
Now that you've said it, i wondered if i should have asked to
check a third set...but too late, my friend bought liao :)
The shopkeeper just explained: 'made in China....' Even though
disrespecting, i think you know what he meant.