Please, my note 4 is with a DRK problem. I have no idea what is it! I've never rooted my phone and i don't want to root it.
Let me try to explain what's going on. The phone is working normal, with android 6.0.1 and there is no problem with the software, but when i try to do a factory data reset through phone settings backup and reset, it automatically goes to the hard reset screen and appears the following sentence:

Supported API: 3
dm-verity verification failed.
Need to check DRK first...

Then i do wipe data factory reset, erase all the things and install the software normally.

Can i just ignore this? Or is there any problem or solution?