iOS 8.4 update causing problems? Here's how to fix them with a full install

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After the iOS 8.4 update, my Phone app kept freezing up while the handset itself was running very hot. A full restore fixed the problems; here's how to perform one.

 

Excerpt:

 

"Like so many other iPhone and iPad owners, I updated to iOS 8.4 last week. As I noted then, the 218 MB update installed without a hitch. I signed up for the budget-friendly Apple Music family plan and went on my way.

Later that day, the problems started.

I first noticed that my iPhone wasn't ringing for incoming calls. Even worse than missing calls, the Phone app kept freezing up; I couldn't navigate between contacts, the dialpad and voicemail. After forcing the Phone app closed a few times, the behavior continued. But that wasn't the worst of it.

 

For several days after the iOS 8.4 upgrade, my iPhone 6 was running hot. Not just warm but hot to the touch; particularly at the top right of the back of the phone and along the right edge. The battery was draining much faster as well; likely coinciding with the sudden heat. Even when in an idle, unused mode, the battery would drop from 100 percent to 50 percent in just a few hours.

 

I tried a few fixes ranging from resetting the phone's settings and forced reboots -- holding down the home and power button for about 10 seconds -- but nothing worked. In the end, I went with what I call the "nuclear" option: Wiping the phone and reinstalling iOS from scratch."

 

He goes on to show how and why in the full article here: http://www.zdnet.com/article/bad-ios-8-4-software-update-heres-how-to-do-a-full-install/?tag=nl.e505&s_cid=e505&ttag=e505&ftag=TRE0fb9d06