New to D700 - is my camera having troubles, or is it me

Hello,

After five years, I decided to change my trusty D70 to a D700, but I'm having some troubles with banding issues in high ISOs and with occasional overexposure when using auto-iso.

From what I've read there, these "issues" are known and normal, but - without searching for it - I seem to get the extreme version of the problem, as shown below :

Sorry about the images quality, I choose the most illustrative pictures, not my best ones

Banding issue :

Shot @5000 ISO, auto-iso, matrix metering, no d-lighting, raw with no processing (other than the obvious raw to jpg and size reduction) :

Nikon support told me this could be a frequency-related issue (just like when shooting a TV at a speed over 1/60), which seems doubtful to me ; I've never heard that sodium vapor lights did flicker at a 60 Hz frequency...

Overexposing issue :

Here are two samples taken (using auto-iso again) on the same day, on a nine seconds interval - framing slightly differs but obviously in less than ten seconds and on such close framing I didn't change the active af (both shots are in auto-iso, matrix metering, no d-lighting, exifs still visible if I didn't mess up)

This one is exposed correctly :

This one is really overexposed, with a 1.3 IL difference from the previous one :

Nikon support incriminates the auto-iso feature there, and advocates against using this.

I can easily understand that getting from a D70 to a D700 is quite a jump in camera complexity, and somehow I hope that the issue is with the photographer, not the camera, but I'm still a bit disturbed since I never had a photo with such exposure troubles with my previous Nikons (from N8008 to the D70)

Thanks in advance for your answers