It might be the air that is used by the automatic shutoff system is all I can think of. I know it pulls in some air to monitor the suction before and after the bag...that air has to be exhausted somewhere. On the older models such as 1205-Ultralux series I know there is an air tube connected to the system that connects and goes right into the closed cordwinder assembly! Never quite understood why this is...but tracking the tube, it clearly goes to the automatic control system.
I have a Lux Legacy...I’ll check mine and see if I get that air at the cordwinder too. I had a Lux Classic which doesn’t have the automatic control system but my Brother has it now across the country, otherwise I would be able to compare to see if it doesn’t occur on the Classic and does on the Legacy, then that would tell me that it’s likely from the automatic control monitoring system for sure. These models are closest to yours as they use the same plastic body.
Which leads me to ask...does your indeed have the automatic control system. I’ve often wondered since I don’t see an adjustment knob for it on that model? Never seen one in person, just on line in pictures. Is it under a cover somewhere? I always liked that particular version of the Guardian, because it is the only one that uses the C bags and has a sleek design to it.
Jon