The Flex had a hesitation and slam at about 60 km/h. This has been a very intermittent problem but previously it was minor. However, a severe slam happened. It's a known problem and Ford has a service advisory. The valve body was replaced.
Transfer case / PTU seal was leaking. Seals replaced under warranty. Noticable improvement in transmission smoothness after repair.
The power-take off unit was leaking. The unit was replaced under warranty. I didn't realize it but this this is the second failure of this unit. The previous failure was repaired under a broader dealer service trip.
Drive train made a horrible metallic snap noise upon first acceleration from park. Dealer found nothing wrong.
Power Transfer Unit (PTU) for AWD system has a known seal leak. Transmission fluid leaks onto hot exhaust manifold and smelly smoke permeates cabin when vehicle comes to a stop. First attempt to repair leak was not successful, despite a TSB.
Second attempt to repair leaking seal in PTU. No problems after this fix...no gear oil leaking onto exhaust manifold ergo no nasty smell anymore!