this is a fix for the rather common build.prop variety problem on nexus 9 (and maybe others). This is the error-message that users often see after boot:
There's an internal problem with your device. Contact your manufacturer for details.
The problem occurs because of a check that google implemented in Android 5.1 which compares /system/build.prop with the values found in /vendor/build.prop. If they differ you get that error message. All one has to do to get rid of the error is to change the 3 values in /vendor/build.prop according to the values in /system/build.prop.
Doing this manually after every flash is cumbersome so I created an update-zip that corrects the values in /vendor/build.prop in a generic way (it should work no matter what rom you use). It mounts /system and /vendor, extracts the relevant information from /system/build.prop and creates a new /vendor/build.prop. I successfully tested it on my nexus 9 so I decided to release it to all of you.
Just install it via your recovery and you are done! This has to be done every time you flash a new rom.
Tell me if it worked for you!