Title: Sibling rivalry

Camera: Nikon Z6II
Lens: Sigma 150-600mm at 200mm focal length
Aperture: f/5.6
ISO: 280 Auto ISO (Yes, I know I shouldn’t have)
Shutter speed: 1/2000sec
Cropped, darkened the background a bit and sharpened with Nik 7 Sharpener Output.
#WildlifePhotography
#BirdPhotography

Question: Would the Auto ISO I used be the reason for the badly distorted branch in the background ? I’ve never had that before, so the only reason I can think of, is the Auto ISO. Its weird though that the top half of the branch is smooth, as expected; bottom half has lots of visual artifacts.