just spent 1 hour with Genius. I have the same problem (same phone as well) did the restore thing but no change really.
But what is annoying is the System storage is showing 6.7G and the Genius said it should be 5G max!!
Also Genius said it was the 1st time in 4 years of working for apple that he had seen this 'other' problem!
The Manager then came over and his phone was showing the same. So something might get done!