Ok folks, I think I might have figured it out. It seemed to be the problem on mine anyway, and perhaps my findings can be helpful to the Samsung tech in figuring out where the source of the problem is (software or hardware).
I contacted Samsung Canada to check on where I could bring it in for service, I was told I *must* take that one last troubleshooting step before they would do that - to do a factory reset, so I went ahead and did that, and it stopped shutting down on the lock screen, so I went ahead restored my data and entered my preferred settings - and it started to happen again.
So, I did a factory reset again - and decided to change things one by one until I found the culprit, thankfully it didn't take long, I started with settings - I like to open my phone with my fingerprint. I changed a few things in the list before that and all was good, as soon as I put in my fingerprint settings - it shut down on lock up. I turned OFF fingerprint access, and it doesn't shut down. I have temporarily fixed the problem by using a different access method - a PIN instead of fingerprint, but I would still very much like to sort out WHY it's broken. It did work fine for over a month - whether it's related to a software update or a hardware malfunction, I still can't tell you, but if you want it to stop now and you use biometrics, try turning them off.
I'll also let Samsung Canada know what I found and ask them for direction, but at least now I'm not going to miss anymore calls.
Cheers - and thanks for your help here.
Thanks for this tip! I had the same problem with my phone shutting off as soon as I stopped using it or locked it. I turned off the fingerprint capability and the problem mysteriously stopped. I would like to know why this bug is happening with the s9.
I had the same problem ,.ok while using but shut down when lock screen.
I did the update apps
Clean cache partition
And nothing happened
Thankfully I came across this post .
I turn off the fingerprint lock screen access and the problem was solved
After that I tried to enter to the fingerprint settings but inmediimmed the phone turned off.
I didn't tried again.
So far so good , but would bring the phone to costumer service.
Thanks for the tip!
This is exactly what is happening to my phone as well! the people at sprint just said it was the factory reset, but got home and it happened again. Any long term fix? Had the phone since march and no problems until two weeks ago
I'm so very happy I found this post.
My phone randomly started shutting itself off today any time the screen would turn off.
The problem persisted even in safe mode, after dumping system cache, while it was plugged in, I changed lock screen from pin and fingerprint to pattern and fingerprint. I turned on the always on display (I didn't have it on before the problem started). I uninstalled the most recently downloaded apps (downloaded over 2 weeks prior to the problem starting). I uninstalled all apps I used today (the day the problem started). Nothing worked.
I backed up the entire phone and was about to factory restore when I stumbled upon this thread. I deleted fingerprint unlock and all fingerprints from the phone. It did screen glitch and turn off during that process three times so I would assume the glitch is in the fingerprint and how it stores the fingerprint data and not on the lock screen itself.
So far so good but I will update if there are any other problems.