What year is your 5.0L?

 

I have a late build 2018 . I would still run the rpm up on that motor some. the chances of getting two bad 5.0 motors is pretty rare. i think the new 10 speed transmission keeps the rpms so low to save fuel the motor never gets to .seat very well . sport mode does a pretty good job at letting the rpms stay up longer then normal mode . I would let it run in sport mode for a few weeks and see if that helps your problem