Default notification changes to "Network Extender" by itself

[Kurt K]

I have a Moto Z2 Force running Android 8.0.0. The default notification keeps being set to "Network Extender". I have manually changed it back to "Missed it" many times. (shade>settings>sound>advanced>Default notification sound).
Apparently at random intervals or events it will change to the "Network Extender" sound. This is not an NFC issue. The notification fires when expected, just with the wrong sound.

 

[jesta192]

I know that can happen when you have the sound file stored on external microSD card. Not sure why it would happen to the built-in sounds, but I remember having a problem kind of like that a while back (the setting would show a numeric name until I changed it back, but it would reset again at some point). I don't even remember which phone it was (maybe Z Force?)

 

[Rukbat]

I've seen that in my Pixel 2. And you get no sound until it's fixed.