Media storage got crazy on my old Android 6 Lenovo phone

[Nafiganado]

I don't know what has happened to my old Lenovo Vibe X on Android 6.01 and how to resolve the issue without wiping data (no guarantee it would help - I'm now thinking...).

The phone is temporarily at my relative's disposal: i've switched to her Google account to let her use my old phone. She complained the call ring was very weak. I decided to change the ringtone, but I found out that I cannot do it anymore, the Media/Audio/Ringtones folder with standard OGG files is not visible (I cannot select ringtones from there anymore). "Other ringtones" option directs me to some installed Audio player, which does not allow to select any MP3 files in ANY folder (they cannot be played, because the player reports they are not added to Media storage). When I try to use "Scan media" option - it is just stuck. I've tried to use another programs like SD scanner, they either report Media database read error or finally report success status, however the audio files are still not playable.

I've tried to: clear caches (Android and Dalvik), disable / enable Media system app and delete its data.

I've also noticed that NOW my USB Audio player reports that HiRes DAC is not found (!) and does not want to play files in HiRes mode (through the chip instead of generic driver) - actually, my phone does have ES9018 DAC...
I am not sure this problem is related to Media storage, however all this together is very weird.

Any thoughts what could happen and what should I do?

 

[blackhawk]

How long was she using it and how good are her Android skills? May have caught a rootkit or virus. Anything below Android 9 is vulnerable to the Xhelper type rootkits that can worm their way out of the user partition. Real nasty critters...
If it just went nuts, I highly suspect malware especially in the hands of a novice user.

 

[ze7zez]

(...) what should I do?

As @blackhawk wrote, the user may have infected the phone.
The only solution is to flash the phone manufacturer's stock ROM.

 

[Nafiganado]

I will try to do this as soon as I get a chance, nowadays there is no other smartphone to use for my relative, so have to wait a couple of days.
BTW - regarding "HiRes DAC is not found" message... is there a chance that guys who replaced the battery in this smartphone soldered out ES9018 chip??

 

[blackhawk]

I will try to do this as soon as I get a chance, nowadays there is no other smartphone to use for my relative, so have to wait a couple of days.
BTW - regarding "HiRes DAC is not found" message... is there a chance that guys who replaced the battery in this smartphone soldered out ES9018 chip??

Likely a software, firmware or settings issue. Malware could also be the root cause for losing the high resolution DAC.
It's possible the tech damaged this circuit but probably not likely. Obviously if it was working before they got their paws on it then they are likely to blame.