[OnePlus 3T Guides, News, & Discussion] the_rooter:
Disclaimer: I have done these steps multiple times and haven't come across any issues, but before you continue please read this fully, and follow the steps completely. Any issues or damage to your phone that occurs while doing this I am not responsible.​

That being said below will be everything you need to make sure this all goes smoothly:

Windows or Linux Laptop/PC

Atleast 50% battery on OP3T

Usb Cable for OP3T

Internet Access

Patience :)

Now to Begin the process to return to stock:

Step 1

: Go to http://downloads.oneplus.net/devices/oneplus-3t/ , and download the 4.0.2 version. Again these are the steps I do so that I can make sure the process is done correctly and also that I can get rid of the annoying dm-verity warning. Don't worry at the end of this you will have the latest version for you're device.

Step 2

: Go to your phone and reboot to twrp, once in twrp go to wipe>Advance Wipe> Tick everything but usb otg (I do this to make sure my phone starts out in a completely clean state>then swipe to wipe. Once it's finished press back twice to get back to the main screen for twrp.

Step 3

: Please reboot device back to twrp. (I found the best way to do this without issues is on the main screen for twrp go to reboot>power off>when the unlocked bootloader warning comes on click the volume up button quickly>use the volume down button when another menu comes on and go to recovery. Again I did it this way because the with twrp version 3.0.4-1 gave me issues when trying to reboot twrp within twrp. Also you will get an No OS installed this is normal as you wiped the system completely. Don't worry just reboot back to twrp.)

Step 4

: Once back to twrp you will get the screen where is says to allow modification. Please swipe to allow. Next please connect phone to pc/laptop, and transfer the 4.0.2 you downloaded to your phone. One completed go back to phone and click install and click on the file you just transferred and swipe to install. Once completed reboot device. (Warning: at this time you will get the Dm-verity warning, but dont be alarmed we will take care of that in the up-coming steps.

Step 5

: Once the phone reboots and comes to the setup screen don't go through and add your accounts because we will be doing another reset. Quickly get to the home screen of your phone and go to settings>about phone>tap build number 7-10 times>back once>developer options>make sure oem unlocking is ticked, advance reboot is ticked, and usb debugging is ticked(If none of them are please tick them). Since your phone is connected to the pc/laptop after you turn on usb debugging a allow authorization box will show on your phone. Please allow that for this to work.

Step 6

: Next go to this link: http://downloads.oneplus.net/oneplus-3t/oneplus_3t_oxygenos_4.0.3/ , and go all the way to the bottom where it says download Oxygen Recovery (optional), and download that file, and place it on desktop.

Step 7

: Now this is assuming you have adb/fastboot setup on you're pc/laptop. Please open up a Command prompt window with phone connected and type these commands in:

1) adb devices ( this will show your device ID Number). If it shows it please continue, if not there is an issue with adb/fastboot set up on your computer, or you typed that command in wrong. Once u get the issue resolved try the command again.​

2) adb reboot bootloader (this will reboot your device to bootloader mode)​

3) fastboot devices ( again this will show your device ID number as from before)​

4) fastboot flash recovery [click and drag the recovery file you downloaded from oneplus website and saved to the desktop here, press enter, and once completed go to your phone and use either the volume up or down button till u see the word Start in green and then press the power button. This will reboot your device, and again you will still have the dm-verity warning on. We are almost done.​

Step 8

: Once your device is rebooted we need to get rid of all traces of twrp so go to your computer>file explorer>this PC tab>your device should be listed there since its still connected to pc> internal storage>locate twrp folder and delete. Now after you are done with this and you want to lock bootloader go to step 9, but if u don't want to relock the bootloader please just factory reset device, setup your device and then go back to oneplus.net and download the 4.03 version and adb sideload it, and dm verity is gone.

Step 9

Relocking bootloader is easy, and will reset your device. While on your phone go to settings>about phone>tap build number 7-10 times>back once>developer options> make sure that OEM unlocking is ticked, advance reboot is ticked, and usb debugging is ticked (again u may get the allow authorization pop up on your phone please allow). Go to command prompt for adb/fastboot and type in these commands:

1) adb devices ( this will show your device ID Number). If it shows it please continue, if not there is an issue with adb/fastboot set up on you're computer, or you typed that command in wrong. Once u get the issue resolved try the command again.​

2) adb reboot bootloader (this will reboot your device to bootloader mode)​

3) fastboot devices ( again this will show you're device ID number as from before)​

4) fastboot oem lock; once you click enter go to your phone, and use your volume up or down buttons to click on lock bootloader. Let finish. This will reset your device again. Once this is all completed and reboot you have gotten rid of all the warning screens, and your device is like it was when you first got it. Set up device with your accounts and you will get a notification of a update. Download and install.​

Congrats your phone is back to stock. If anyone has questions please pm me.

Again these steps are longer than what most of you may do. A few others including myself have done this multiple times to confirm. None of us had issues. It works

**Special Thanks**

The guys that tested this with me to confirm my steps are accurate

Google for well google :)

Oneplus for yet another awesome device and software.

***UPDATE***

Thanks to [MENTION=4791945]ashokmor007[/MENTION] he made the video below on the steps.

https://www.youtube.com/shared?ci=xDFI-287K-Q