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I've observed this problem after updating iPhone 5 to iOS 8: single click the home button would sporadically bring up the multitasking screen, instead of going back to the home screen. This appears to happen regardless of what app I single click the home button in.

I have since performed the following:

1) Settings / General / Accessibility / Home-click Speed both at Slow and Slowest
2) Settings / General / Reset / Reset All Settings
3) Restore using iTunes, set up as a new phone

The issue persists.

I have then downgraded back to 7.1.2. The issue no longer appears. So this does not appear to be a hardware issue.

Anyone else seeing this?
 
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