FaceTime Audio Disappears mid-call

Hi there, I've been recently noticing a problem with my FaceTime calls. When I make calls, about 15 mins into the conversation, everything just goes quiet. The call is still indicating it's connected, but there is no audio at all. I can't hear anyone talking nor can they hear me. I have to end the call and re-dial it; the SAME thing occurs! This seems to happen MOSTLY at night, but I am experiencing it constantly, on the At&t network and WiFi -- I'm assure why or what could be causing it. It's really frustrating, I can't make any call without this happening, if you just stay on the call it stays completely silent, the only solution is to end the call and redial. This of course only gives you a short amount of time to talk to someone ( if you want to have an extended conversations, 2 + hours)

Of course I didn't have these problems ever on iOS 7...

This happens using an iPhone 6 Plus, the person I call has an iPhone 5S -- I am running the most up to date software, their phone is on iOS 8.1 I believe. (Unsure if this could be an issue...)

Here is what I know so far:

What fixes it:

Ending the call and redialing it

A iPhone reset tends to prolong this audio disappearance for a half hour/hour tops.

When it goes silent, the call still displays as connected, no interference, just the usual call static.

Is this is a documented problem? I tried searching everywhere for answers; I can't seem to find any. I hope someone has some news on this! Thanks