Upper taking too long heating

I am not finding any information for this issue with this unit. No service pointers found. The ovens normally will take about 20 mins give or take to preheat. The higher the set temp the longer it will take. Are they turning the ovens on both at the same time with the same set temp? I would just make sure both bake and broil elements are working. This model should use the broil elements to preheat as well. Does one oven have convection and the other now? Could they be using convention bake on the bottom and not the top? Heat from the lower oven when using both at the same time can effect the temps in the upper oven. I would not be concerned with the longer preheat time if everything is working correctly and temps are correct.