Nexus 5x - No one can hear me on the phone I've had this phone since November and it's still in great condition. From the start though call quality hasn't been amazing, friends often tell me that I'm very quite (I'm not actually speaking quietly). In the last few days though absolutely no one can hear me unless I have my headphones plugged in but even then it's not ALL the time that it works. The headphones don't have a mic so it's nothing to do with them I imagine. I've made a few videos to check that it was still recording sound and it works perfectly still. It's really left me baffled. While the phone is still in warranty I really do want to avoid sending it to LG as I don't have a backup phone. 

Does anyone have any idea what could be causing this? I'm running stock vanilla 6.0.1  I don't have a case on the phone (I've seen a few people complain their case covers up their mic), neither I've muted the call (I've tapped the mute button a few times to make sure).
I had this same issue with my HTC One. It turned out that the background noise cancellation software build into the phone canceled out too much (thus cancelling out my voice). This especially happened when it was windy outside.

That being said, I haven't heard of this being an issue with the Nexus 5x. I would start with contacting Google support.