I had the same problem. I still do, but I kind of covered it up. Since I don't change the sim card often, once every 6 months. I crazy glued the sim card tray to the body. I did not use a lot of crazy glue but just enough to hold it in place. If you are going to follow this, make sure to get a crazy glue that can be removed by something like nail polish remover. Now, if I have to change the sim I just use nail polish remover and scratch away at the glue to get the tray out and crazy glue it back in.
I've come up with an idea how to fix this. Simcard tray for n9 for about 10 times more expensive than that for lumia 800 but lumia's too short and n9 doesn't see the sim card. So I bought a simcard tray for lumia 800 and switched the plates inside so that the plate where simcard is hold is from n9 but the cover is from lumia 800. Works like charm.
I have other solution for this. I had for few days lumia 800 sim card slot and it fits ok inside N9, it didn't stands out. So i find out why, inside sim slot there is some kind of spring on left side(touchscreen side), lumia 800 slot is shorter than n9 so it didn't touch this spring. So here is solution
Left leg should be cut off about one milimeter, it's metal so you can't use scissors
Now it didn't stands out, yes I have broken usb door new one is coming from store now.
