Exact model number : Pixel C (yeah... actually)
Installed OS : Stock android 8.1.0 Oreo
Platform : Unity 2017.3.0f3 with built-in Vuforia extension, OpenGLES2 graphic API only + Device filter set to ARMv7 "only" just to rule that out
Device orientation : both
Front / back camera :
did not try works fine on front camera, not on back camera
Samples : any / all
Occurence vs. Internet connection : no difference
The app launches once without problem (apart from a camera focusing problem which can easily be circumvent), if the app is closed, the camera playback never works again.
The device can be rebooted, shut down, the camera playback is black.
The tracker recognition still works though, and the 3D AR objects appear in the black void.
The only solution is to uninstall the app, and install it again. At this point you can use it one more time, before you need to uninstall it again.
(Not sure if the bug tracker is the correct one, but right now, i was not able to build using sdk command line tools 26, have to replace with 25 for it to work with this version of unity)
edit : not related
The problem cannot be reproduced using the exact same tablet running Stock Android 7.1, it works as expected using android 7.1
Also the same App works fine on a wide variety of android devices (android 6 and 7)
Thanks in advance,