HELP! Problem with my new NEX-F3?

Hello all,

Just got a brand new NEX-F3. Im happy with it overall, but theres some banding in high ISO situations that I dont know if it's common or if I got a defective camera. It's mostly common when taking photos with both automatic modes.

Enough talking, lets go to the samples: 

Automatic mode, no flash. Able to see the banding?

Manual mode. No flash also, higher expo time.

Thats it. Banding often appears when shooting at low light situations in automatic mode (but not exclusively) and without flash. Defective camera? Am I doing something wrong?