Convection Oven Preheat
We have a 2015 Berk with the Whirlpool convection oven too. While preheating to cook some biscuits, it took a full 30 minutes to finish the preheat and get the beep. It just showed "preheat" on the screen the whole 30 minutes. I put the biscuits in about 15 minutes into the preheat cycle and they were almost done by the time the oven thought it was preheated!
Please post back after you talk to Whirlpool and let us know what you learn.
By the way...welcome to the forum, this is my first post too!