[Q] Nexus 9 bootloops with every ROM other than stock. - Nexus 9 Q&A, Help & Troubleshooting

TL;DR: Nexus 9 bootloops with every ROM other than stock.
My Nexus 9 will bootloop whenever any custom ROM is installed on it. I follow the usual steps in TWRP (downloading ROM and Gapps, wiping factory reset, flashing the zips and wipe dalvik/cache) will not get any error during installation and regardless of the ROM, I will get my nexus stuck on Google logo. Then I will have to unroot and install stock again and it'll work.
Ive also tried Wugfresh Nexus Root Toolkit and it won't work either. As long as Im on stock, I can root as well and everything is fine.
Any idea what could be happening? I wanna get rid of the damn lag. Have tried Cyanogenmod, Slimrom6 and Pure Nexus Project. All with their recommended gapps and will always end up with my tablet stuck in the Google logo.
Any help is very appreciated.

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Sounds like you are doing everything right..
How long are you waiting for the device to start up ? Is it possible you aren't simply waiting long enough ? I'd give it a good 10 - 20 minutes on 1st boot before deciding it's hung in a boot loop.

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I am having the exact same problem. I have tried so many roms that install correctly and then when flashing gapps and rebooting it is stuck on the Google logo. And I left my tablet on for a few hours so its definitely bootlooping.

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The only thing that comes to mind is bootloader... If you coming to androind 7.x from android 6.x, you need to flash new bootloader (for example via ADB), otherwise you'll end up in a bootloop.

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yup, happening to me too. so, how can i flash the factory image now? thanks.

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It's in the stickies. http://forum.xda-developers.com/nexus-9/general/guide-how-to-unlock-bootloader-flash-t3035153
Sent from my Nexus 5X using XDA-Developers mobile app

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links to 7.x compatible bootloader where?
maelfilk said:
If you coming to androind 7.x from android 6.x, you need to flash new bootloader (for example via ADB), otherwise you'll end up in a bootloop.
Click to expand...
Click to collapse
I understand that i'll have to use adb (actually fastboot) to flash the bootloader. But where do i get the right one for android 7.x and flpunder device?
Could you please post the links for that?
Thanks in advance!

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nexacan said:
I understand that i'll have to use adb (actually fastboot) to flash the bootloader. But where do i get the right one for android 7.x and flpunder device?
Could you please post the links for that?
Thanks in advance!
Click to expand...
Click to collapse
You can download the necessary image here: https://developers.google.com/android/images
Inside the archive you'll find bootloader and vendor

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bootloader flashing process: enough to "fastboot flash bootloader boot*.img"?
maelfilk said:
You can download the necessary image here: https://developers.google.com/android/images
Inside the archive you'll find bootloader and vendor
Click to expand...
Click to collapse
I assume i need the latest 7.0.0 (NRD91N, Nov 2016) bootloader which is inside the latest build?
Then i will need to go through the process like:
Code:
fastboot flash bootloader bootloader-flounder-3.48.0.0141.img
Or do i have to do more like described here (Steps 8-9)?
Your help is appreciated, thanks again!
ps: for others who got stuck in the bootloop and don't know how to stop it or turn off the device:
1. reboot into recoverymode in case you have twrp
2. open a terminal
3. type in
Code:
poweroff
an hit enter

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Yes, NRD91N
Well , all i did was simple
fastboot flash bootloader bootloader-flounder-3.48.0.0141.img
once complete
fastboot reboot-bootloader
That's it

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Still not booting...
maelfilk said:
Yes, NRD91N
fastboot flash bootloader bootloader-flounder-3.48.0.0141.img
fastboot reboot-bootloader
...
That's it
Click to expand...
Click to collapse
Thanks for clarifying that. Unfortunately i still can't boot into AOSP_flounder_11-18-2016.zip
which i flashed afterwards. The bootloader is shown correctly though. But when i start the
Nexus 9 the message https://g.co/ABH is shown in red.
Which rom are you running? A CM build or AOSP?
ps: trying with cm-14.1-20161027-UNOFFICIAL-flounder.zip now, but boot seems to hang too and the upper part
of the Nexus 9 is getting really warm. I will leave it for 15 more minutes to wait and see what happens.

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nexacan said:
Thanks for clarifying that. Unfortunately i still can't boot into AOSP_flounder_11-18-2016.zip
which i flashed afterwards. The bootloader is shown correctly though. But when i start the
Nexus 9 the message https://g.co/ABH is shown in red.
Which rom are you running? A CM build or AOSP?
Click to expand...
Click to collapse
Hmm sorry i don't knwo why this is happening.
Currently i reverted back to marshmallow roms, i find them more stable.
Do you have twrp? After flashing bootloader i go to twrp and do complete wipe and format data, then flash new rom. I had no problems booting.

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maelfilk said:
Do you have twrp?
Click to expand...
Click to collapse
Sure, the latest from TWRP
twrp-3.0.2-1-flounder.img 13M 2016-08-24 16:30:03 EDT
maelfilk said:
After flashing bootloader i go to twrp and do complete wipe and format data, then flash new rom. I had no problems booting.
Click to expand...
Click to collapse
I will try it again - exactly as you describe it. Maybe i missed a step.
How long did you wait after reboot for the system to start up?

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nexacan said:
Sure, the latest from TWRP
twrp-3.0.2-1-flounder.img 13M 2016-08-24 16:30:03 EDT
I will try it again - exactly as you describe it. Maybe i missed a step.
How long did you wait after reboot for the system to start up?
Click to expand...
Click to collapse
About 10-15 minutes

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It works now!
Thank you maelfilk, i got i running now.
CM boots properly now - though i cannot configure it. During the Setup process
in the first step of selecting the language it crashes. I am sure this will be fixed
with a later version of CM-14.1.
Does someone know any other source for CM-14.1 for flounder?
Meanwhile i will try AOSP again.
Edit: AOSP boots properly but unfortunately WLAN does not work in the AOSP_flounder_11-18-2016.zip build.
I guess this is why you stick to the 6.x builds maelfilk.
большое спасибо

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nexacan said:
большое спасибо
Click to expand...
Click to collapse
Glad it works
As for wlan problem, did you flash the vendor as well? If not it might be the problem

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link to the "vendor"
maelfilk said:
Glad it works
As for wlan problem, did you flash the vendor as well? If not it might be the problem
Click to expand...
Click to collapse
Man, you are so helpfull! Where do i find the "vendor" (drivers?) please?
I guess i will find it as it is described here

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nexacan said:
Man, you are so helpfull! Where do i find the "vendor" (drivers?) please?
I guess i will find it as it is described here
Click to expand...
Click to collapse
In the archive with bootloader is another archive with vendor and other images. Just flash it in twrp as in the instructions in the link you gave. If you have trouble with wlan or camera it usually means that vendor is outdated.

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Black bootscreen and hanging after flashing vendor.img (only vendor.img)
maelfilk said:
In the archive with bootloader is another archive with vendor and other images. Just flash it in twrp as in the instructions...
Click to expand...
Click to collapse
I did that and now there is no bootscreen, and the Nexus 9 does not boot up
Maybe i am missing something again? I did a wipe and fresh install, but that did not help.
Also TWRP disappears after flashing vendor.img

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nexacan said:
I did that and now there is no bootscreen, and the Nexus 9 does not boot up
Maybe i am missing something again? I did a wipe and fresh install, but that did not help.
Also TWRP disappears after flashing vendor.img
Click to expand...
Click to collapse
Are you sure you chose to flash vendor.img in vendor partition in twrp?