Top of cake puffed and collapsed
I baked a coconut pound cake yesterday. It was a low heat 325 bake.. It looked beautiful when I took it out of the oven. It did take a little longer to bake than the recipe specified. I put it on a rack to cool and when I went back to it the top had collapsed. Obviously it had puffed up during the bake but when I tested it there was no indication of that. The cake itself was good but did show some moist spots when sliced.
I'd appreciate any feedback on what might cause this. I've had it happen before with other things. It wasn't for a contest but all the same presentation is important too.
The rising agents were a tsp of baking powder and six eggs. Wet ingredients were yogurt, coconut milk and two sticks of butter. Dry were flour, sugar, salt and the baking powder.
Thanks for any help on this.