crumbcake error -- cake overtook crumbs

[nantastic]

Baked Exploration's NY style crumb cake is currently in my oven, and when turning the pan 180 degrees, I noticed that the cake had swallowed up the crumb topping. I've made this cake multiple times and this happened once before and I'm not sure why. Am I overbeating the cake dough? Are my crumbs too big? Any ideas?

[cheesecake17]

That happened once when I made a Martha Stewart crumb cake. The next time, I baked the batter a bit before adding the crumbs.