[denkweb]

Preventing this problem is possible as well, a very easy way of prevention is to make sure you can still open the glovebox when the pin in the switch breaks while it is locked.

Get yourself a little, thin, black wire, about 10cm.
Attach this to the pin which sticks out of the lock itself (a small piece of metal).
This piece is the part that get's behind the latch as mentioned above and actually locks the dashboard.
After attaching, lock the dashboard and let the wire stick out. When pulling the wire a little bit, the lock should open.
take a little of black tape and attach the wire on top of your glovebox, just in reach when needed. Cut off the rest of the wire (or leave it inside).
You can always open the glovebox now when the lock doesn't work no more!

This issue is a very common problem on the 850/x70, so be smart and use this trick shortly!

Drawed some images I had stored as well to show my intentions:

 

[denkweb]

There also is another way to open the glovebox.

You then need to exchange te cover afterwards....

Drill a 2mm hole 2cm of the top edge of the cover and exactly in the middle of the cover. You then can reach the lever (on which to ty the wire in the instruction above) from the outside with a small screwdriver. Press it through the hole and it will open.

you can replace the cover or fill the hole with something and paint it in the colour of your dash again.