Phone keeps crashing, then restarting s21+ 5g

[thefad3done]

Probably started about 4/ 5 months ago, my phone started to randomly crash. Sometimes when using it. Other times it would do it when not being used.

What tends to happen is the phone freezes, screen goes black. Then it vibrates and restarts, taking an age to start sometimes and every now and then the one ui will do its app optimisation thing.

On occasion, random apps will start to crash before the full crash occurs. I.e I'll be on Instagram or on chrome (or literally any other app), and it'll close suddenly and not repoen. I try to open anything else and the same until suddenly full phone crash & restart. I also have had it crash on the restart itself where only the samsung logo appears and it doesn't continue to load (where the secured by knox logo then appears) and I have have to force it off with the button presses. There appears to be no pattern to the crashes and i can go days or weeks without issue or I'll have multiple instances of this occurring over and over in just a few days

The phones still in warranty and I've had Samsung out to look at it but couldn't find any faults with it. Even the device care app says "your phone restarted recently" but doesn't list any faults or issues whatsoever. None of the "tests" ever find an issue. It is doing my head in as I cannot figure out what the issue is or what's causing it.

Everything I have tried:

Apps are up to date (both stores including making sure android Web viewer and google play services updated as i have seen this mentioned lots)

Factory resets have been done many times

Cache clearing in the bootloader options

Safe mode

System updates applied

Have also tried not installing any additional apps other than stock, still occurs.

I've ensured that the restart occasionally option is turned off (and still is)

Gone through the diagnostic stuff on device care with no issues showing

Had and engineer out, found no fault on tests so didn't do anything although on the phone they said it was likely a main board issue.

Starting to lose my patience with, the otherwise lovely, phone.

[Eastgate]

Hi did the above fix the issue? Everything you have mentioned above are the same issues I have with my s21 ultra.

[thefad3done]

I've not had a single crash so far since the main board and usb replacement. I had that switched out on the 11th September via wefix technician that come to me. The Important thing was not wiping the phone like support tell you to do, as this also wipes any error logs. Without those logs I'd still be going mad with the crashes like 3 months ago when I had wefix out then.

Fingers crossed it stays working as normal now, but ever since the work was done I haven't had any kind of crashes at all. Its been working perfectly.

[Eastgate]

Nice one. Mines a refurb so I'm just going to return it as not worth the hassle. Shame as it's a great phone other than it restarting itself twice a day.

[Qingzue]

Had this problem on and off, on many different a or s series, samsung know, they just don't care. My s21 was fine, the black Friday sales start and my phone starts crashing again:/

[elielina]

Hi, Im having the exact same problem on my S21+. Did the replacement help? 

[thefad3done]

Yep, not had an issue since Samsung replaced the mainboard. Phones worked perfectly ever since

[AB455]

I'm not surprised they kept telling you to wipe the phone constantly. There can't be a problem if there's no problem to be found, eh? 

I got a used S21+ for Christmas this past year and I have not been able to get through a single day without it crashing. It does the exact same things described here by everyone that's had the problem. It crashes constantly, I'd say 4-5 times a day that I'm aware of. That's not counting every time it goes down while I'm not using it. I'll just pick it up and it'll prompt me to draw pattern after restart. I've decided I'm switching to OnePlus, f#$k this mess.

[Mukesh097]

Happened to me after I started my Wifi. If Wifi is off then everything works fine. When the power key and volume up-down keys are pressed then it doesn't enter into the boot menu. Nothing worked and it kept happening in the loop until the battery was dead. Then somehow it reached the OneUI page and the optimizing apps thing happened, after that, everything was working fine but as I turned on Wifi again the same thing started happening again. 

Device: Samsung Galaxy M42 5G