This may be caused by two things:
Disable NVIDIA AI Denoising completely.
Note: it has to be disable in two places to disable it for interactive and non-interactive rendering:
- Render Setup > Scene > Denoising > Mode (set to "None" or some other denoising type)
- Render Setup > Performance > Interactive rendering > "Fast preview denoise during render" checkbox (disable it)
2) Image upscaling factor
You can disable the image upscaling factor in Render Setup > System > System settings (set it to 1.0).
If the above solutions did not help, please contact us about your issue.