[Google Pixel 2 XL Questions & Answers] PMad:
I purchased my Pixel 2 XL from the Google store. I had just upgraded to the 8.1 OTA a few days before when i came across this video and used it to root my phone:

https://youtu.be/nFD9sa-WdUM

Here's the basic steps i took:

Unlock dev options and turn on OEM Unlocking

Boot to stock recovery

Go to his highonandroid site and download TWRP 3.1.1 beta2 (img and zip), an outdated fastboot.zip, magisk 14.5, and the USB drivers which i didnt download because my computer is already recognizing my device just fine.

Extract the fastboot files to a new folder and copy the twrp img file to the fastboot folder.

In CMD, unlock the bootloader with fastboot and reboot phone.

Connect phone as storage device, copy over twrp zip file and magisk 14.5 zip files to root folder on the phone, reboot into recovery

Use fastboot to boot the twrp image that we copied to fastboot folder to get into twrp

Unhook the USB cable, set TWRP to read only, install TWRP, hit home button, then install Magisk and reboot

Once booted up, get into Magisk, download proprietary software, run checks and done.

Once this was done, my fingerprint scanner and wifi no longer worked. I could turn wifi on but it would never find anything. I also received the error when rebooting the phone that says "There's an internal problem with your device. Contact your manufacturer for details." When this message is on the screen, if i dont touch the phone and the screen times out, it flickers really bad and never actually shuts off until i unlock it and hit the OK button.

So i decided to give it another go and ran into some big issues. I figured that i used 8.0 instructions on 8.1 and there was enough things different that it caused problems, so i used this link to reroot:

https://xdaforums.com/pixel-2-xl/how-to/guide-unlock-flash-root-pixel-2-xl-t3702418

I went through the first 10-15 pages and the last 10-15 pages and did some searches on the thread and never found any of my issues, but found that a lot of people used different sets of steps and pretty much everything was successful as long as you didnt miss anything and used the most updated stuff. So i did, i went to googles website and downloaded the newest SDK with fastboot, adb, and all that good stuff, as well as the newest 8.1 image (there was a newer version but it had a carrier label on it so i didnt get that one), and the newest magisk and twrp.

I flashed 8.1 and the phone wouldnt boot, nor would it get into TWRP anymore, so i had to use fastboot to boot the twrp image and reinstall the recovery and magisk but it still wouldnt boot. I ran through several different steps and eventually got it to boot up with recovery working. Its the newest 8.1 image, the newest magisk, and the newest twrp, and since then magisk has updated a couple times.

Now on to my issues!

I still get the "Internal problem" popup when booting

I get a lot more random reboots

Sometimes random things just wont work, like streaming plex to my tv or loading an app or something on an app and i have to reboot and it works fine

I've seen numerous times that the "Internal problem" thing is just a mismatch between the system and vendor build.prop files. I dont know what exactly is mismatching between the two but i've tried reflashing them and all sorts of things and nothing ever fixes it.

Does anyone know if there's a fix to any of these three issues, or if maybe looking at my steps i clearly did something wrong? I'm willing to do the whole thing over again if there's a good suggestion, but once i flashed the 8.1 image and went that route, i rerooted successfully 4 times total before i quit doing it again just because of that internal problem popup, i kept figuring something went wrong or i did something wrong. I had no security or anything set before rooting or flashing or anything, and each time i reflashed the operating system, but when i flashed the OS, i had to extract the system file because i would constantly get an error that it was too big and it failed to truncate it, so i've always had to manually install it by first copying it to my phone and installing it through TWRP. Its been an adventure, but these problems suck!