Hi. I'm in Australia, and many people here are experiencing the same issue, only with a twist.
When calling an overseas contact, Facetime forks fine for both parties. Then after about 10 seconds, the video of the overseas contact will stall and blank out with an error message about 'poor connection'. Audio remains good at the overseas contact, Home (Australian) contact retains both good audio and video.
This occurs whether the Home contact uses an iPad on wifi, or Mac Mini on ethernet.
I work overseas and use Facetime to call my family back home in Australia each night. It has worked perfectly for years, but since Christmas it has become unusable.
I can make Facetime calls from my location to the UK no problem, but family calling from UK to Australia, and NZ to Australia are also experience the video crashing. Apparently (I've heard from other sources), domestic Australian calls are ok.
I've tried changing the DNS settings of the home device, no good. I've tried using a vpn on the home device, no good.
I've run out of ideas, and patience and had give up on Facetime. I now use Skype, that works fine.
Strangely, I upgraded both the MBP (mid-2012) that I use when travelling, and the home Mac Mini (2011) to El Capitan as soon as the OS came out, but only started to experience the above issues with Facetime video in December. So perhaps they're not related after all.
Any advice on a potential fix would be greatly appreciated. This really is doing my head in!
Cheers.