Oh my god - I had the exact same problem, but I didn't post it here since I thought I must be missing something very obvious.
My driver's side headrest was all the way down initially. Then I pulled it up, but it won't go back down! There is now always 1" space which is quite annoying. It was much more comfortable with the headrest all the way down. Ofcourse, I can't test anything since my car is being shipped at the moment, but thanks for bringing this to everyone's attention.