iPad Issue with Notif./Control Center and four-finger swipe up

[linbetwin]

I've had an iPad Air for seven months but recently, after installing iOS 8.0, I've had some software issues: Sometimes Notification Center and Control Center do not come down/up when I swipe with my finger from the homescreen or from an app. Sometimes they do work on the lockscreen, sometimes they don't. Also, when this happens, swiping up with four fingers doesn't bring up recently used apps. I've tried turning Multitasking Gestures on and off, but it didn't help. I've even done a full reset and set the iPad as new, with no luck. The only thing that fixes these issues is a reboot, but they inevitably reappear later.

I hoped that software updates would fix this, but 8.0.1, 8.0.2 and 8.1 did not help. iOS 8 fixed a screen orientation bug from iOS 7, but introduced these new bugs.

Any ideas ?