There should be a vacuum switch for the exhaust blower but that wouldn't relate to the convection blower turning on - that is a heat-related function. Good idea though to check the line on vacuum switch to ensure it is not cracked or split. While vacuum switches can fail, it is rare. How is the door gasket? Haven't looked at the manual again - is there one on the ash pan and/or hopper lid?
They will smoke a lot before ignition
As long as you have no smoke leakage, your exhaust blower appears to be doing its job. The large initial amount of pellets will generate a fairly large flame initially but that settles down once started and is then under the control of the auger setting.
With more pellets, did the convection blower start as it should? Or did you have to do the restart? What exactly do you use for starting procedure? Pre-soak pellets with hand sanitizer/starter gel? It may be just a matter of hitting the sweet spot with amount of starter gel and amount of pellets...