Why does my phone freeze/restart even in recovery?

[t_CARQQUK]

My Note 5 (SM-N920C, running stock Nougat) keeps freezing and/or restarting. It does so in virtually any context:

- after loading into Nougat
- after loading into stock recovery
- even when powered down and charging

After anything from a few seconds to several minutes, it will either freeze (stock Android and stock recovery), will not wake up if the screen was off (stock Android) or will simply restart (in any situation). It may either freeze outright, freeze for a minute and then restart, or just restart. When it does the notification LED starts usually as white on boot. When it's frozen only Volume Down + Power will restart it.

Only when it's on the download screen (Volume Down + Home + Power) will it work without fail. The "Odin mode" never freezes or restarts.

I've flashed thoroughly, even going so far as to wipe Dalvik, system, cache, etc in TWRP before directly restarting into download and flashing a clean firmware with Odin.

The buttons work fine and switching off NFC or WiFi doesn't help.

It seems to me to be a hardware issue. Unfortunately, the Note 5 was never released in the EU so there aren't (m)any repair shops that have the parts to just fix it.

As the download screen never freezes, it seems unlikely to be the battery.
As recovery is also affected, it seems unlikely to be the EMMC.

Given all of this, does this sound familiar? What might need replacing?

 

[Rukbat]

First, an Android phone is set up to triple-boot (the way you can double boot on a PC, choosing Windows or Linux at boot time) - there's one partition for recovery, which is a minimal Android OS, one for download, which is an almost non-OS and the third for normal (and safe mode) boot. So any one or two can go bad and you can still use the other.

Which is a good thing, because you can back up everything when it's working (even if you have to restart a few times) - see Backing up an Android Device - then reflash the ROM (see [Samsung] How to flash Stock ROM via ODIN). SamMobile has a load of Nougat ROMs for the 920C, so you should be able to find yours, flash it, then restore everything. (Restore your apps one at a time and play with the app for a while, to make sure it's not one of your apps causing the problem. You might even restart in safe mode first, to see if it is an app. If not, back up and flash.)

 

[Tim1954]

Ah! You sure know your stuff Rukbat! I am impressed! ??????

 

[t_CARQQUK]

I may have been unclear: I've flashed the Note 5 thoroughly, but it hasn't helped. Please see my initial post for details.

 

[t_CARQQUK]

In the end, it turned out to be a motherboard issue. Whatever caused the phone to operate without issue occasionally for a while, the problem wasn't completely fixed until I switched out the motherboard.