I had a long phone call today with Apple support about my problem loosing the sound fully and having pop noises when I put my SIM-Card into the iPad Air2. They did take the logfiles about conflicts and crashes directly from my device and found a lot of conflicts. Finally after looking at all they told me to reset it again to factory settings, to set it up again and then try. It did work Sound with SIM card is back. So they told me they have such cases, something wrong in the backup. They told me I may not use the backup to restore the device or I will get the problem back again. That is really nice, doing all from zero again, building the App groups and so on. I must all do new and it works fine, pop sounds have gone. I believe something in the backups went wrong and as everybody always uses these backups when buying a new device to restore it the problem get's bigger. At least I deleted my backups now and setup the iPad from scratch. A lot of work, but if it works then it's worth it.
Fritz