Hello, Folks. I am new to this forum, but thought it useful to describe my experiences with the MKX. Let me state at the beginning that the car is great, my wife loves it, but being a beta tester for a new model is always a bit of a slog.
Our first problem materialized when the car was less than one year old and the dreaded transmission oil leak where the passenger side axle enters the PTU materialized. After 4 visits this was finally resolved. The dealer replaced the PTU seal twice before realizing that the seal replacement was not an option for the 3.7L configuration. The solution was to replace the PTU and the axle shaft.
A year later, another 11k miles, another transmission oil leak. This time it was the seal on the input shaft for the PTU. The seal was replaced yesterday.
Several other things of note. First, the sulfur/rotten eggs smell on acceleration. We had it big time. It turns out that there is apparently a TSB which entails taking the rear bumper off, sealing a bunch of stuff, and replacing some vent inlets. Time will tell if this worked.
Finally, on start-up we often got a headlight error showing up on the left instrument cluster. Turns out that early build MKXs (ours was 7/27/15) there is an issue with the HCM. The claim is that the reprogramming should fix this.
So, hopefully all the bugs are worked out. But if you have any of the problems above, rest assured that you are not alone.