I recently bought 2 Blackview BV6000 phones and have same problem on both. During longer calls sometimes sound on microphone gets gradually lower to a point where you barely can hear. Usually if you drop the call and call again it gets better. Sometimes need to restart phone. Updated both, did factory reset - the same. What I noticed is that when it happens it's usually it switches to 3g network from 4g - don't know if it can be connected.
Any ideas? Is that a common issue? Any fix available? Or more troubleshooting? Getting close to a point where will need to return both and get different brand phones
Or is this same thing as with loudspeaker?