Forum My torte caprese sinks!

Hi all, 

I have recently made the torte caprese from the Everyday Cookbook, which I unashamedly admit is one of the most delicious chocolate cakes I've ever scoffed. However during baking it totally collapsed and sunk in the middle. I was baking it for an occasion so I made another and was super careful not to bump the tin or oven and didn't open the door during cooking in case that was why the first one sunk, but again, it totally collapsed. It rose evenly to start with but then got to a point and deflated (along with my baking confidence). Has this happened to anyone else? Does anyone have any suggestions? Other than sinking, it baked evenly and still tasted amazing, it just looked terrible