I wanted to chime in, I had this same issue with 422 10bit mov files on S5II only importing into premiere pro cc 2018 as audio files, no video. I did a bunch of tests and figured out it could import video files with audio when filming horizontal, but when I would film vertically it would only import the audio file.
The fix:
Gear icon in menu > lens / others > go to bottom "Vertical Position Info (Video) and set it to "OFF" and it actually fixed the issue.