Okay, so here are the next steps.
1)
Install this app, OTA Snatcher this app will make a copy of your OTA which based on your system version 9.16.6 the OTA will be labeled something like "Blur_Version.9.16.6.XT926.Veizon.en.US" - I'll get to this step in moment for now download this app.
2)
Install the app OTA Rootkeeper, this is to backup Root.
3) Go ahead and make all of your backups to this point, you will need to do an FDR, and this will erase all Data and everything. So make your backups of the apks, I should note that you will most likely only be able to restore the data on each individual apk, I don’t know what you’re using. If you are backing up the System and Data as a ROM Backup, if the OTA is successful you will not be able to use the ROM Backup as this OTA changes the System version and Baseband, restoring a backup would remove the new System version and Baseband.
4) Go into OTA Rootkeeper and “Temp-Unroot” then go into Settings> Privacy> and hit the FDR.
5) Go ahead and reapply your settings, and get your apps installed, once OTA Rootkeeper appears go ahead and Restore Root, if Root fails let apps continue to load. If Root has failed and once all apks have been updated and installed, go into the App drawer find the SU Hashmark app, hold down on it and Uninstall it. Once it has been removed go into Motochopper and reinstall Root. This will only work on System versions 9.16.6 and 9.16.9. Let device boot and go ahead and make sure SU is working.
6) Now that you have Root and have the Unlocked Bootloader, go into Settings> System update> and begin to download the OTA. But do not install, yet.
7) Once, OTA has downloaded go into OTA Snatcher and select the option to snatch the OTA. Pay attention to the location as the OTA is saved on the Internal Storage. In order to find the OTA which will be labeled "Blur_Version.9.16.6.XT926.Veizon.en.US" you need to have a file manager on your device, just find the file> then cut or copy the file and paste it on your External SD Card or SD1> do not place the file in a folder it should be located where the files such as “data”, “DCIM”, “LOST.DIR” are located.
8) You will need to stock recovery to precede this produces the most consistent results, if you are unsure of what Recovery you have it is most likely that you stock recovery.
9) Go ahead and go to your app drawer> find OTA Rootkeeper> select and “Temp Un-Root” save your SU Backup and go ahead to Settings> System update> select Install.
If all goes well, then your device will reboot and the new System version will 9.18.79 and the Baseband will be VANQUISH_BP_100730.160.15P.
If the OTA fails here is what you do.
10) Go ahead and Reboot> Power + Volume (-) down> as soon as the screen goes black hold Power + Volume (+) up> highlight the Recovery option and press Volume (+) up> at the dead android screen hold Volume (-) down and quickly press Volume (+) up. Now find the option to install update for external memory and press the Power button> this will open your sd card find the file "Blur_Version.9.16.6.XT926.Veizon.en.US" and press Power.
This may or may not work, but what is important is to get the error messages if it fails. Downloading the OTA through the System updates does not generate an error message, just mentions installations is aborted or install fails. Installation from the SD card, or Sideload, or ADB if there is something that fails then it is important to note what exactly fails, so it can be fixed or completely redone. Also, even if the update fails, still check your Settings> About phone> and what the System version and Baseband are. Sometimes the update will fail however it pushes enough information over to partial install or fully install the update with an installation failure.
Don’t forget to restore Root with OTA Rootkeeper when all is done, if it doesn’t work, let me know and I will post a Restore Root method for after OTA completes.