1, your oven is baking temperature is high more, resulting in the external has been baked dry, the internal is still soft, the remedy can only be to reduce the baking temperature, extend the baking time to see if it can work.

2, the oven baking temperature is low more, baking time is not enough, more baking time can be good

You are new to buy the oven, we recommend that you do a temperature calibration, especially mechanical thermostat oven, baking temperature deviation will be relatively large