S7 (SM-930F) echo on phone calls but not VoIP (Whatapp etc)

[papadeltasierra]

Samsung - can you explain what's up with my wife's Galaxy S7?  Callers are hearing terrible echos on regular voice calls.  Things that I know:

• UK phone, latest UK firmware
• Tried a complete factory reset and wipe but this didn't make any difference
• Tried enabling and later disabling "concert mode" but this didn't make any difference
• Tried placing fingers of the various speakers and mics but this makes no difference
• Callers hear echo even if my wife is using a plugged in head-set, which makes me think this cannot be a hardware mic/speaker issue
• VoIP calls such as Messenger or Whatsapp are fine with no echo, which also makes me thing this is not a hardware mic/speaker issue
• My daughter has the same model phone, same firmware etc but her phone works fine
• Wife and daughter on same UK network (Vodafone contract).

So is there some hidden software setting that is causing this and if so, how do I fix it?  Or what else do I try to diagnose the fault?

FWIW I'm a software engineer so quite happy getting "down and dirty" to fix this - for example I know what to do with "odin" ;-).

Thanks,
Paul DS

[truckergod]

I don't believe samsung is sending out software updates for the s7 anymore. The best outcome would be if the mic was at fault.

[papadeltasierra]

According to my wife, this only started about 3 weeks ago which makes me suspect some sort of software issue maybe caused by an updated app.  Must check if my daughter has updated her apps lately.  In the meantime, I tried:

• swapping SIMs between my daughter and wife's phones (both S7s, same firmware) but this made no difference.
• tried removing the  SDcard in case there was some bizarre "buffering via card" or similar happening; no difference.

This is almost certainly software issue (see notes about external headphones etc) but I'm at a loss to see what :-(.

[papadeltasierra]

Other things we have tried:
1. Turning the sound on my wife's phone down to "zero" - echo on caller's end is just as bad

2. Booting to safe mode - echo just as bad.

#1 implies this has nothing to do with hardware and #2 implies this is a Samsung bug (I believe not 3rd-party software should be running).

Anyone from Samsung monitor this thread and able to comment please?