When you 7 inch full screen 2din android car stereo have volume buttons faulty, please go to factory settings, put the "hcttouch" click OK, then the screen will display 

android car stereo buttons faulty

Then please take some picture to show the screen when you put the  "hcttouch" click OK by rambojoying@gmail.com

We need to confirm the problem is software or other.

Any more questions please contact to support@carjoying.com