FaceTime audio half duplex / doesn't work simultaneously

Question

I gave my parents a new iPad Air for Christmas.  Note: They are 'older' and have a lot of trouble operating electronic devices.  Before sending it to them I did check for recent updates, set up their email and contacts, installed some apps that I  find useful and uploaded some photos.  Otherwise it's a fresh unit right out of the box. 
Yesterday we tried facetime with them.  The video worked as it should.  The audio seemed to be in a 'half duplex' mode on our device.  Meaning, they could hear us perfectly and normally on the iPad.  We could only hear them when we were perfectly quiet.  Any sounds or talking on our end would mute their transmission during and about 1 second after speaking.
We tried multiple calls.  (I called them and then they called me).  We tried an iphone 5 and a MacBook, the problem was consistant in all cases.  During one of our calls on the mac, my brother placed a facetime call to my phone and his connection worked perfectly, while my parent's connection continued to have the issue.
I sent them the following instructions, in hopes that it may fix the issue, but I'm doubtful.  I don't have an iPad handy (only iphones and the mac in our house) so there may be some settings that are present on the iPad and not on the iphone that they should try.  Any and all help would be appreciated!   They live on Kauai, HI so if there are any places there that would be helpful that they could visit, I would appreciate the recommendation.
Go into settings, scroll down until you see facetime. Select it. There will be some settings for facetime. One simply says facetime and there is a small green slider button next to it. Touch the button. It should slide and turn white. This disables facetime.
Go to settings, then general, then software update. It should say "checking updates" and then will either display your version (7.0.4 ?) OR it will say there is a new update and you can download it. If so, download/install. (Should be a button asking and just hit yes or ok).
Next, do a network reset:
Go to settings, general, scroll down to "reset". Select reset and then select "reset network settings". It will ask if you want to do this and yes, you want to do it.
Next, After all this is done, reboot the ipad. This is done by pressing and holding the top (power/sleep) button and the home button down at the same time. Hold it for 30-seconds maybe longer until the screen goes black and then the apple logo appears. Then let go.
(If you hold just the upper button for 5 seconds a red slider will appear to allow you to turn off the ipad. For a reset just ignore that and keep holding down the buttons).
Once it reboots, add yourself back to your network. It may ask on its own, but if not :
Go to settings, then wi-fi. Select your network and enter your password.
Last, go into settings, general, facetime and turn it back on by touching the white slider button. It should turn green.
I found two other cases that sounded like mine:
https://discussions.apple.com/message/22808569#22808569
https://discussions.apple.com/message/22705969?searchText=Facetime%20duplex#2270 5969

Answer 1

My parents called apple tech support.  I'm not exactly sure what they did, but I think they just rebooted the iPad again, as done previously.  It seems to be working better now, although it does still cut out now and then from sounds on my end of the line.
Another thing that seems to have helped, I determined that my parents had left it in the original plastic packaging and then crammed it into the case I gave them, which may have slightly muffled their microphones. 
Anyway between these two things it is working better.  We can speak on this end and still hear them talking.  But now and then it still cuts out.