[Nexus 6P Q&A, Help & Troubleshooting] defcomg:
The Problem is the Active Area DNG Tag the darker area should not be visible somehow Active Area Tag is conflicting with Default crop size tag http://www.barrypearson.co.uk/articles/dng/specification.htm. dcraw based apps seem to use active area tag and ignore the default crop tag so the band is not visible

6P DNG Header

ExifTool Version Number : 9.69
File Name : ProShot_20151126_143708.dng
Directory : C:/Users/GeorgeKiarie/Downloads
File Size : 24 MB
File Modification Date/Time : 2015:11:26 22:20:33+02:00
File Access Date/Time : 2015:11:26 22:17:54+02:00
File Creation Date/Time : 2015:11:26 22:17:54+02:00
File Permissions : rw-rw-rw-
File Type : DNG
MIME Type : image/x-adobe-dng
Exif Byte Order : Little-endian (Intel, II)
Subfile Type : Full-resolution Image
Image Width : 4080
Image Height : 3028
Bits Per Sample : 16
Compression : Uncompressed
Photometric Interpretation : Color Filter Array
Make : Huawei
Camera Model Name : Nexus 6P
Strip Offsets : (Binary data 25901 bytes, use -b option to extract)
Orientation : Horizontal (normal)
Samples Per Pixel : 1
Rows Per Strip : 1
Strip Byte Counts : (Binary data 15139 bytes, use -b option to extract)
X Resolution : 72
Y Resolution : 72
Planar Configuration : Chunky
Resolution Unit : inches
Software : google/angler/angler:6.0/MDB08L/2343525:user/release-keys
Modify Date : 2015:11:24 01:13:03
XMP Toolkit : Adobe XMP Core 5.6-c011 79.156380, 2014/05/21-23:38:37
Creator Tool : google/angler/angler:6.0/MDB08L/2343525:user/release-keys
Rating : 0
Metadata Date : 2015:11:26 14:46:24-04:00
Date Created : 2015:11:24 01:13:03
Document ID : E76921AC715FABD3C153F15B23AEEA74
Original Document ID : E76921AC715FABD3C153F15B23AEEA74
Instance ID : xmp.iid:42b35b1d-eeff-ea44-a7be-becf042fbc8c
Format : image/dng
Raw File Name : ProShot_20151126_143708.dng
Version : 9.3
Has Settings : False
Has Crop : False
Already Applied : False
Photographic Sensitivity : 100
History Action : saved
History Instance ID : xmp.iid:42b35b1d-eeff-ea44-a7be-becf042fbc8c
History When : 2015:11:26 14:46:24-04:00
History Software Agent : Adobe Photoshop Camera Raw 9.3 (Windows)
History Changed : /metadata
CFA Repeat Pattern Dim : 2 2
CFA Pattern 2 : 0 1 1 2
Exposure Time : 1/110
F Number : 2.0
Exif Version : 0221
Shutter Speed Value : 1/110
Aperture Value : 2.0
GPS Version ID : 2.3.0.0
GPS Latitude Ref : North
GPS Longitude Ref : West
GPS Time Stamp : 18:37:11
GPS Date Stamp : 2015:11:26
ISO : 100
Date/Time Original : 2015:11:24 01:13:03
Focal Length : 4.7 mm
TIFF-EP Standard ID : 1 0 0 0
DNG Version : 1.4.0.0
DNG Backward Version : 1.1.0.0
Unique Camera Model : Nexus 6P-Huawei-google
CFA Plane Color : Red,Green,Blue
CFA Layout : Rectangular
Black Level Repeat Dim : 2 2
Black Level : 52 52 52 52
White Level : 1023
Default Scale : 1 1
Default Crop Origin : 8 8
Default Crop Size : 4016 3008
Color Matrix 1 : 0.8125 -0.2265625 -0.125 -0.3203125 1.265625 0.0390625 -0.0390625 0.2265625 0.453125
Color Matrix 2 : 1.0078125 -0.2890625 -0.21875 -0.5625 1.6328125 -0.046875 -0.0703125 0.2109375 0.640625
Camera Calibration 1 : 1 0 0 0 1 0 0 0 0.9921875
Camera Calibration 2 : 1 0 0 0 1 0 0 0 0.9921875
As Shot Neutral : 0.46875 1 0.6328125
Calibration Illuminant 1 : D65
Calibration Illuminant 2 : Standard Light A
Active Area : 2 48 3026 4080
Forward Matrix 1 : 0.578125 0.21875 0.1640625 0.15625 0.84375 0 -0.015625 -0.2890625 1.1328125
Forward Matrix 2 : 0.6875 0.015625 0.265625 0.2109375 0.6796875 0.1015625 0 -0.5390625 1.3671875
Opcode List 2 : (Binary data 3908 bytes, use -b option to extract)
Opcode List 3 : (Binary data 4 bytes, use -b option to extract)
Noise Profile : 0.00020673168 1.8208447e-006 0.00020673168 1.8208447e-006 0.00020673168 1.8208447e-006
Aperture : 2.0
CFA Pattern : [Red,Green][Green,Blue]
GPS Date/Time : 2015:11:26 18:37:11Z
GPS Latitude : 13 deg 4' 13.48" N
GPS Longitude : 59 deg 33' 59.05" W
GPS Position : 13 deg 4' 13.48" N, 59 deg 33' 59.05" W
Image Size : 4080x3028
Shutter Speed : 1/110
Focal Length : 4.7 mm
Light Value : 8.8

Moto Nexus 6 DNG Header

ExifTool Version Number : 9.69
File Name : paraiso.dng
Directory : C:/Users/GeorgeKiarie/Pictures/DNG/other
File Size : 25 MB
File Modification Date/Time : 2015:08:04 02:07:42+02:00
File Access Date/Time : 2015:08:04 02:04:32+02:00
File Creation Date/Time : 2015:08:04 02:04:32+02:00
File Permissions : rw-rw-rw-
File Type : DNG
MIME Type : image/x-adobe-dng
Exif Byte Order : Little-endian (Intel, II)
Subfile Type : Full-resolution Image
Image Width : 4208
Image Height : 3120
Bits Per Sample : 16
Compression : Uncompressed
Photometric Interpretation : Color Filter Array
Image Description :
Make : motorola
Camera Model Name : Nexus 6
Strip Offsets : (Binary data 26769 bytes, use -b option to extract)
Orientation : Horizontal (normal)
Samples Per Pixel : 1
Rows Per Strip : 1
Strip Byte Counts : (Binary data 15599 bytes, use -b option to extract)
X Resolution : 72
Y Resolution : 72
Planar Configuration : Chunky
Resolution Unit : inches
Software : google/shamu/shamu:5.0/LRX21O/1570415:user/release-keys
Modify Date : 1970:01:22 17:47:12
CFA Repeat Pattern Dim : 2 2
CFA Pattern 2 : 2 1 1 0
Copyright :
Exposure Time : 1/1653
F Number : 2.0
ISO : 40
Date/Time Original : 1970:01:22 17:47:12
Focal Length : 3.8 mm
TIFF-EP Standard ID : 1 0 0 0
DNG Version : 1.4.0.0
DNG Backward Version : 1.1.0.0
Unique Camera Model : Nexus 6-motorola-google
CFA Plane Color : Red,Green,Blue
CFA Layout : Rectangular
Black Level Repeat Dim : 2 2
Black Level : 64 64 64 64
White Level : 1023
Default Scale : 1 1
Default Crop Origin : 8 8
Default Crop Size : 4200 3112
Color Matrix 1 : 0.6953125 -0.0859375 -0.09375 -0.4609375 1.296875 0.1328125 -0.109375 0.2578125 0.5390625
Color Matrix 2 : 1.21875 -0.4296875 -0.25 -0.4609375 1.5 0.015625 -0.046875 0.21875 0.609375
Camera Calibration 1 : 1 0 0 0 1 0 0 0 1
Camera Calibration 2 : 1 0 0 0 1 0 0 0 1
As Shot Neutral : 0.5390625 1 0.6640625
Calibration Illuminant 1 : D65
Calibration Illuminant 2 : Standard Light A
Forward Matrix 1 : 0.7578125 0.0859375 0.1171875 0.2734375 0.828125 -0.1015625 0.015625 -0.28125 1.0859375
Forward Matrix 2 : 0.6328125 0.046875 0.28125 0.1640625 0.7578125 0.078125 -0.046875 -0.640625 1.5078125
Opcode List 2 : (Binary data 3908 bytes, use -b option to extract)
Noise Profile : 0.00051471478 0 0.00051471478 0 0.00051471478 0
Aperture : 2.0
CFA Pattern : [Blue,Green][Green,Red]
Image Size : 4208x3120
Shutter Speed : 1/1653
Focal Length : 3.8 mm
Light Value : 14.0

when opening nexus 6 dng in PS /LR the image res is 4200 x 3112 but on dcraw based apps res is 4208 x 3120 now had moto added Active area tag i believe there would have been a dark area on pixels that go past 4200.

on lightroom pc DNG Recover Edge plugin should make it go away .

it would be interseting to see how the header of a 5x or 6p without that issue looks like