iTunes not able to recognise photos storage on iPhone

I have synced new photos app with my iPhone. I have around 5k photos which I am syncing with iPhone.

The photos are syncing fine but iTunes is not able to recognise the storage for iPhone. It reports 4GB of other storage along with photos storage. I have tried resetting and other stuff but still that extra 4GB is there.

Something it just says 0 photos and 4GB extra and sometime it shows 8GB (4GB photos and 4GB extra)..

Anybody else facing this kind of strange issue with iTunes.

I am using iPhone 6 Plus with Macbook Pro. I have iPhone 6 also which I am syncing with the same macbook and its working fine.