In the latest iOS updates, did Apple change the way Airplay communicate with other devices through Wifi?

Short :

In the latest iOS updates, did Apple change the way Airplay communicate with other devices through Wifi?

Detailed:

We had a glitch with our Apple TV 3A 3-4 weeks ago and had to factory reset it (we reconfigured it with the exact same configuration than before the crash), it's now running iOS 7.0.2, I can't saw which version it ran before the problem though.

It's used in a business environment with 30+ iPads 2, half of them are updated to 8.1.1 and the other half to 8.1.2. We use the latest iTunes version.

Before the glitch that required a reset, all the iPads were detecting and mirroring when needed to the Apple TV, but now the iPads don't see the Apple TV in their list of Airplay devices anymore (but they detect various other devices inside our network).

I have to add that our Apple TV is able to navigate the movie store correctly, so I assume that it's not an internet restriction issue from our end (also, the APple TV do not see either any of the many iPads on its device-detection screen.

We successfully connected an iPhone 5S and an iPhone 6 through P2P Airplay, so it's not the issue, but when we connected the iPhones to our Wifi network (Same as all the other devices are using) the Apple TV suddenly disappeared from the choices.

Hence the reason why I inquire to the possibility that some changes were made in one of the latest iOS revisions, if so, we would require some details so we can adjust our Wifi configuration accordingly to allow the proper detection of devices.

P.S. I tried the basic troubleshooting of Airplay problems with no avail. Airplay button is displaying on the control panel, Airplay do not show the Apple TV at all (so it's not either the trick to display the Mirroring button), we also already proceeded to the suggested devices reboots, so my issue is quite more complex I believe.

Thanks in advance.