How to get the PCMCIA slot to hold the card again?

I ejected a PCMCIA card that I was using in the upper slot, by pushing the two buttons in the case. Now when I try to insert it again, it doesn't stay put. I've been looking with some light inside, but can't see nothing weird or different to the inferior slot.

How can I unlock it again without having to dismantle the whole thing, is there a way? At least, it seems to me that when you remove the heat shield you can see the interior of the module. But I don't know what to look for.

Any help is much appreciated. It's the first time this happens to me, and while I can still use the inferior slot, I would like to use them both.

Thank you!

Ok, after a couple hours I learnt that you can use the little hole beside the slot, not only to release a card but also, to release a locked mechanism. So I inserted the end of a paperclip, heard a noise "Ding" and it was working as always again…

Hope this helps someone.