[Laurent Fluttert]

Thanks Joakim, but no, it’s not the scaling. I tried all scaling options but they all result in the banding in the blur.
I tried what would happen if I put blur on the shot in After Effects: also banding! (And I made shure that input and output settings were 4K 10 bit).
I rescaled the shot outside of Resolve, made it RGB 10bit, but again in Resolve, the banding occured.

I worked around it: the blur was intended to make a radiator less prominent; now I removed the blur but also removed the radiator from the shot (in after effects). Problem solved (sort of).

[Laurent Fluttert]

No, it is not a monitoring issue. Monitor is 10 bit. Also, when I’m making the blur, no banding is visible on the monitor.
Only when I export or when I switch to ‘edit’.