This vent was full of lint.  Once lint collects in the gooseneck on the roof, it prevents excess lint from the dryer from exiting the dryer vent, and this causes a rapid blockage.  We were able to remove all the lint from the vent, but because the dryer had an accordion style foil transition vent, the air velocity was still low, which would have lead to premature buildup moving forward.  We were able to install a DryerFlex on the dryer, and now it’s operating efficiently and safely and won’t need to be cleaned again for another 2-4 years.