lid not opening when I press the release catch

Hi all,

Not a great problem really but my 2008 old style macbook pro (which I really like still) has one annoying thing. The lid closes properly but when I press the button to release the lid it doesn't spring up like it used to. The mechanism works and releases the hooks but I have to lift the lid while holding the button at the same time if you know what I mean. Any ideas appreciated. I don't mind taking it apart - I've done it few times before.

Thank you