Ear Problem

My new oven is quite big and because of my new baking stone that slightly bigger my oven door cannot closed almost as tight as it was (but not very open either) this is where I noticed that suddenly it became very hard for me to get an ear even though I have a great oven spring. Recipe:- Bread Flour (13%) 560gr- WW Flour 140gr- Water 560- Cocoa Powder (Bloomed) 280gr- Levain