I remembered different in-camera settings and now checked and tried all of them with my D750
- Setup Menu → Auto Image Rotation On/Off
- Playback Menu → Rotate On/Off
and took pics with the release button
- upwards = 270° CW
- downwards = 90° CW
In no case I got your strange ‘result’, where PL5 showed the pic in vertical orientation and SEP3 processed it horizontally (but Viv2 and SEP2 vertically).
And yes, like @George and @Joanna checked with ExifTool, you must have tried / correct something in Capture NX and/or PM6 …