Help Can't get screen lock sounds off

[Pekka]

I just switched from a Galaxy Trend Plus (Android 4.2 Jelly Bean) to Galaxy J5 (Android 5.1 Lollipop), and the thing driving me nuts the most is the bleep-blop sound the machine makes almost every time I wake the screen up either from sleep or from lock (now I realize I do not get it when I lock it up even with Screen lock sounds turned on). I have disabled all system sounds (and restarted the device after), tried to disable every single sound except ringtone, making the default notification sound Silent, but no. Bleep-****ing-blop.

The only thing that makes it go away is dialing all notification sounds silent on the volume knob, but I'd rather like to be notified about text messages and such. So the thing is under notifications dial and not system dial.

Is it a bug or am I just not getting something?

 

[Pekka]

The thing seems to act very randomly at times. I thought I had it beaten by disabling the power button lock (I have the J5 Flip Wallet by Samsung, and I've been battling its auto-lock feature, which I managed to disable by disabling the power button lock and instead relying on the automatic lock timer) because after making that change the bleep-blop was gone for a few good relaxing hours. Now it's back, and sometimes coupled with another bleep-bloppish kind of sound. Maybe a bli-blip.

I scrolled through the list of notification sounds in the device settings, and found neither of these noises, so maybe it's caused by some app or whatever that manages to mask it as a malfunctioning screen lock sound with its timing? The only widget I use is the weather/clock thing which I removed for a second with no results. Maybe something network related? I'm on wifi at home, and I can't say for sure that I get the sound while I'm away...

...So, better try disabling wifi for a second and see... Ok, it looked promising at first with a b-b noise coming perhaps twice on the first fifteen trys, but then it just kept coming every time I turned the screen on. So Wifi I guess is out of the question.

 

[Pekka]

Since only muting all notification sounds seems to work so far, I tried blocking notifications from every single app on the device. But no. So it must be somehow system based.