AMy yellow cake recipe I've used for years has just stopped turning out right. I haven't changed any brands or amounts of ingredients, it's always assembled the same way, and I replaced my leavenings just in case they were no good. My oven is new and the other cakes come out great. It rises in the oven and looks fine but when I pull it out is sinks and is dense and wet in the middle even though a toothpick comes out clean. Every time. I've added more batter to the pan, still fell. I've baked it longer, tried different temps. Nothing. It just failed me AGAIN on a plain old sheet cake. I'm going to run the cake over in the street a few times before setting the recipe on fire.

Any idea what I'm doing wrong? Has this happened to anybody before?

AGet an oven thermometer....something might have happened to the thermostat?

AHumidity has arrived and your flour is not in air tight container?