I had the same issue, wifi disconnecting intermittently and thus affecting my airply soecially when im connected to vpn. I was about to send my iphone to service center to have it checked as my phone is the only one having issues while other devices are connected to wifi and stable. Well service center here will do diagnostics, software and hardware repait before recommending for unit replacement. Good thing i stumbled upon this thread and adding DNS helped. Wifi and airplay is ok and not disconnecting. Will continue to monitor for stability. Thank you.