You own a Nexus device mostly to be able to customize your device to your liking, without the limits posed by locked bootloader. But some Nexus 9 users are getting a curious error when they have flashed a custom ROM of their choice. The error is: “There’s an internal problem with your device. Contact your manufacturer for details”, and is caused due to difference between build.prop file under the system folder, and the same under the vendor folder.
So, yes, the fix is obvious. You have to change particular 3 contradicting values and make their values same in both files. You could do it yourself, but luckily, and thanks to gladiac, there’s a flashable zip available that would do the job for you once and for all, so that you don’t have to do it on each reboot. Cool, right?
How to: You’ll need a TWRP recovery on your Nexus 9 for this, of course. Get it here, if you don’t have it. Then download the fix from here (file: vendor-build-prop-fix-signed.zip) and transfer to your Nexus 9. Then reboot into recovery mode, select Install, select the file (vendor-build-prop-fix-signed.zip) and use the Swipe action at bottom to install it. Go back and reboot the system. That’s it. you shall no longer see that error.