Bootlooped 30min, then came back. Memory corrupted? How do I check?

[RFZ]

Okay, today evening, my Nexus 5X rebootet already 5 times while I was using it just as every evening (browsing web, watching youtube, nothing special).
After the second reboot, it actually vibrated two times during the boot animation (after entering the decryption pin) like it usually only does when powering it up.
After the third reboot, it bootlooped for more than 30min (!!) ... Just the bootloader (white google logo), then ~3s black screen, then vibrating and Google Logo again!
Entering boot menu was possible... I used it to power off and reboot, but didn't help. I was just letting it bootloop while I searched my old Nexus 4 to reactivate it
After the 30min or more bootlooping (by the time I already found my Nexus 4 and reinstalled its battery ) the Nexus 5X asked for decryption pin.... I entered it, it rebootet. It asked again. If finally bootet.
After ~3min of use (just enough for a whatsapp backup) it rebootet again and bootlooped again for ~15min. And same again.
Now it is back once again - for the moment.
I need help, what can I do now, except backing up all relevant data?
It is stock android, not rooted, bootloader locked
Can I somehow test the memory? See why it rebooted?
It NEVER rebooted before since I own it...
Thx

 

[RFZ]

The device rebooted after few minutes yesterday... It still overcomes the first bootloop from time to time after dozens of bootloops but then crashes most of the time after I was able to enter the pin. Since yesterday, it only managed to finish booting two times but always rebooted after few minutes.
Is this the famous BLOD? Haven't heard of it until today (sorry) ...
I actually had OEM unlock enabled in the developer menu, so I could actually unlock the bootloader...
Can I verify that it actually is the BLOD by unlocking the bootloader and temporary booting the modified boot image using fastboot? I don't want to flash something at the moment, because I might get it replaced... I can lock the bootloader again afterwards, right?

 

[nowster]

I think it might be possible to use "fastboot boot boot.img" (using the 4-core kernel image) from the bootloader screen. That won't install anything.

 

[RFZ]

Thx. However, it requires me to unlock the bootloader and delete all data, since there is no 4-core kernel provided/signed by google, right? I will be able to lock the bootloader again afterwards, as long as I won't flash a different kernel (or reflash the stock kernel), right?

 

[caifaz]

dude while your phone is on, first backup your files, then enable OEM unlock, if your phone is damaged with bootloop of dead, you will be able to make it work using the 4 kernels fix.

 

[RFZ]

dude while your phone is on, first backup your files, then enable OEM unlock, if your phone is damaged with bootloop of dead, you will be able to make it work using the 4 kernels fix.

I do have all important data backed up, I guess. Doing Backups for Android is just PITA... I wasn't able to get the phone running for more than a few minutes today. OEM unlock is enabled, but the bootloader is locked still, so all data will be deleted. I'll try the 4 core kernel as soon as I completely restored all data to my replacement phone, so I'm really confident I can wipe all data from the old one.
Thx so far!

 

[caifaz]

I do have all important data backed up, I guess. Doing Backups for Android is just PITA... I wasn't able to get the phone running for more than a few minutes today. OEM unlock is enabled, but the bootloader is locked still, so all data will be deleted. I'll try the 4 core kernel as soon as I completely restored all data to my replacement phone, so I'm really confident I can wipe all data from the old one.
Thx so far!

you're welcome, there is no need to flash a bootloader, just flash the TWRP recovery (modded for 4 cores), restart to recovery and then flash EX kernel (modded for 4 cores) according to you SO version.

I have fixed a phone 2 years ago using this instructions

 

[RFZ]

Okay, I just verified it... The device boots fine with the 4 core kernel. I then reflashed the stock image, locked the bootloader, and it bootloops again. Will send it back to the store now and hope I'll get a refund/replacement :fingers-crossed: