Why does my iPhone 6s Plus keep glitching during FaceTime audio/video?

Can anyone tell me why my iPhone 6s Plus keeps glitching during FaceTime audio and video? It also sometimes restarts on its own. I'm very concerned with what's going on- it's not an old phone and it hasn't had any problems since I've had it.

  • Why won't my iPhone record audio when I take a video? Every time I try to record a video with my iPhone it won't pick up the audio. All I here is this static noise. Sometimes I can barley hear my voice behind all the static. It just randomly started happening. When I record in voice memo it picks up my voice just fine. Phone calls work fine too. It just doesn't work when I try to take a video.
  • Why does FaceTime Audio sound better with mute on? I ll FaceTime Audio call my girlfriend from my iPhone to hers at night. When it's quiet like if she falls asleep, I can hear her for a bit and every now and then it gets silent. It's not because she stops breathing it just happens. When I hit mute on my end though, I hear everything and the sound never drops even for a second. Why is it that with mute?
  • What is FaceTime audio on iPhone? I have never used it but out of the blue today it notified me that some random number added me. What is it? How or why did they add me
  • Other person can't hear audio on FaceTime? I was FaceTimeing my sister and she said she couldn't hear me, that my audio would cut out and then come back and repeat. I can hear her perfectly fine and the picture is good. She tried on her Mac and iPhone and they both didn't work.I'm on my iPod and I did a test on my camera and the audio was okay. I'm not covering the mic and I'm not on mute. I thought it was lagging too. Her Wi-Fi at school is not that good and she doesn't get good service out there.