Diagonal banding in the dark frames ZWO ASI585MC Pro · marsaz · ... · 5 · 307 · 2

Hello,
I've just bought a ZWO ASI585MC Pro, my first cooled astrocam. Didn't get the chance to test it outside yet due to cloudy weather (of course) but I made some dark and bias frames, checked the cooling works, etc., and I've noticed this weird diagonal banding. Only visible in the dark frames, no sign of it in the bias frames. Also, it seems to be less visible at lower temperatures and pretty much disappears when the camera goes below 0C. I couldn't detect it at -10C at all.
Given this is a new camera, should I worry about this and try to return it? Or just shoot as is with it cooled?
Any guesses what could be causing this? I've tried moving cables around (thinking it could be some sort of interference), different USB ports and different computers. Same result, seems like something in the camera is causing it. The bands appear to consist of noise only, but I can't say for sure, and are exposure length dependent - banding is more pronounced the longer the exposure is.

Here are the dark frames, you can clearly see the bands taken at room temperature and no sign of them at -10C.

Room temp, 252 gain, 120 seconds

Cooled to -10C, 252 gain, 120 seconds

Sebastian:
Hello marsaz,

Yesterday I took darks with the settings you mentioned, there was no banding.

During my first darks, some light fell into the telescope because the lids weren't closing properly.

There were 2 horizontal stripes - these weren't as clearly defined as yours. Can you rule out extraneous light? Can the camera be replaced? Unfortunately, I can only upload images with a maximum of 1Mb..... Here is a link to Google Drive where you can get the images.
Just strech it.

https://drive.google.com/drive/folders/17_0j4rCvnlq2av5pPCVrBfaKJbWTOX7I?usp=sharing

Greetings,
ebastian

I understand this is NOT supposed to be there, I don't know if this warrants a return though. It's not a light leak either, I've tried different things, I couldn't get the bands to move or change intensity based on where the camera is (even tried putting it in a black backpack with caps on, etc.). The bands disappear by cooling the camera without changing anything else. I can also calibrate them out using a temperature matching dark. I just want to test it out during an imaging session to make sure it doesn't affect the stacked images.

I have that camera and have never seen this issue.