@OrangeNebula Looking at your screenshot it looks like many layers including a layer group containing that layer effect. Plus the obvious dithering, what format is the image, RGB or Indexed ? Both open and when exported.
Helpful if you can post the affected file as a Gimp .xcf or maybe give a more complete screenshot of the layer dock. The Brightness-Contrast layer effect can be applied as previous Gimp by ticking the "apply" option in the tool dialogue (or merging in the layer dock). Does that make any difference ?
Helpful if you can post the affected file as a Gimp .xcf or maybe give a more complete screenshot of the layer dock. The Brightness-Contrast layer effect can be applied as previous Gimp by ticking the "apply" option in the tool dialogue (or merging in the layer dock). Does that make any difference ?