Color-Banding Darks ASI 294

LsdDonut

Hi you guys, hope you can help me out.
Since yesterday i am getting strange banding pattern in my darkframes with my ASI 294 MC Pro Color.
Due to bad weather i havent used this cam as much as i wanted. Maybe 15-20 nights.

These patterns did not occur to me the last times. Darkframes where more or less homogenically covered terms of color-noise.
Temperatures outside where 0° to -5°Celsius. Camera was cooled to -20°C, with a cooling power of 30%.
Gain 120 ; Exposure Time 30secs.
I am afraid these patterns where dramatically impacting my postprocessing.
Something wrong with the cam?

Thank you very much for the support.

3 pictures where attached.

LsdDonut

After further testing, those blue bands only appear if the ambient temperature drops below 0°C.
Test-shots inside the house turn out to be fine.

Does anybody have the same efects?
Anyone who can test it outside in the cold?

Thank you very much,

Clear Sky !