Serious duct issue -- discovered by my Bosch!
This is a picture of my dryer duct up in my attic. Thank goodness for the E01 error message on my new Bosch 500 series dryer, or I may not have known about this until I'd had a dryer fire! It appears the builders of our house ran out of tapered ends, so they just smashed a regular round end on a standard 4" piece of ductwork. The resulting hole is maybe 1" square, and resulted in a lot of lint getting trapped in the duct!