I would check out that secondary HE on the furnace. The AAV is the cousin to Carriers SX series furnace in which we have been finding alot of bad secondaries. Pull the blower and and look up into the secondary compartment and look for water trails/corrosion. You can also look into the drain areas and see if you find chunks of plastic/pvc. Were either of these contractors Bryant dealers? If not, I would find a Factory Authorized Dealer for Bryant and have them inspect the system. If they were Factory Dealers, I would be calling Bryants (800) 428-4326 number to their consumer affairs dept. and get a little better service/explanation from that/those company(s).