Have they run any hardware tests to confirm it was the hardware? Are you restoring these from backups or have you tried starting fresh?
All Apple suggested was to "forget this network" then set up again. I've also reset the iPad's but always restored from backup as i have stuff I don't want to lose. I'm now thinking it's not the iPad (3 faulty? surely not) but the wifi. It only occurs in my bedroom. Downstairs it's never lost the signal. I also spoke to my wifi supplier and they just suggested changing the channel number in settings. Still no good...
[doublepost=1463841534][/doublepost]I've just found this on Apple website. I've changed the DNS to 8.8.8.8 as suggested and so far it's working. Don't understand what this does but I'l give it a go.
"General suggestions for Wi-Fi issues, maybe one of them will help.... Since it is new, I would try 1-7 and if not successful I would go back to the Apple Store. I would not do a restore on a new device.
1) Perform a Forced Restart: Hold down the Home and Wake/Sleep buttons at the same time for about 15-20 seconds until the Apple logo appears. Allow device to restart.
2) Reset Network Settings: Settings > General > Reset > Reset Network Settings. Rejoin the Network again.
3) Change to Google's DNS: Settings > Wi-Fi > Click on the Network, Delete all numbers under DNS and enter 8.8.8.8 or alternatively 8.8.4.4
4) Disable the QoS service on the router if available.
5) Reboot Router/Modem: Unplug from power for 2 minutes and plug again. Update Router Firmware (check manufacturer’s support website). Verify your router is Wi-Fi certified.
6) Determine if other Wi-Fi devices on network are working well (other iOS devices, Macs, PCs).
7) Try device at another Network, i.e., neighbors’, public coffee house, etc.
8) Restore the Device (ask for additional for details if desired)."