I recently made a pumpkin sheet cake with cream cheese frosting. The cake had crunchy “things” throughout. Felt like you were biting down on ground glass, but nothing was apparent to the eye, and no ill effects on the digestion. Could this be undissolved sugar? Only white sugar was used.
You didn’t post a recipe so I will wing it here - did you use dark pans to bake your cake in? Did you pack down the flour when measuring it? Did you beat it too long? Did you bake it too long? Is your oven calibrated? Did you use improper measuring cups? Did you add the right amount of liquid? Did it dry out?