Glad you have heat. Strange that it didn't put out heat on the defrost setting even after 10 min, maybe the heater valve was stuck and became unstuck after a couple heater cycles?

Another tid bit I recall from my e28, the recommended setting to defrost was high heat and high fan with the middle and footwell vents closed but the windshield vents open. This was manual HVAC controls. I think our cars do all of these setting automatically with the front defrost button. Makes sense, as hot air will warm the windshield and prevent condensation from building up. I wish we had the heating elements in the front windshield for defrost.