Two Thermador burners out -electric

Two heater-element burners on our Thernmador range have gone out in the last two weeks. We had a service person here and he determined that the heater-element needed to be replaced. It was a dual-element burner…the outer ring stopped heating up but the inner ring was ok. Now another burner has gone out.

Could this be a coincidence or some other issue that should be looked at??