MP Ultra Magnus Leg fix?

So, I just got a minty fresh MP Ultra Magnus for Christmas (yay!), only to open up the box (which has previously been sealed) and find that one of his legs wont stay extended.. it keeps wanting to slide up. i had a fiddle with it and i can hear something rattling inside the lower leg part, so i'm guessing a spring or something has come loose :(

Any ideas how i can fix this, apart from sending it back to the seller and getting a new one?

it's possibly something you can fix yourself. My mp prime had the opposite problem, his leg wouldnt retract because the gas tank tab was too large and i had to sand it down a bit, its possible that the tab on yours has come out of place.

Cheers Kup, i took apart the big guy's leg and the tab had snapped, so i've just put superglue on it and will see how it goes :)