Pixelised gallery images

Hi, Images look blurry and pixelised when going for "original size" with catch plugin. Didn't have this issue before, but maybe last update. I can get clean carousel pics when going for another size but the gallery doesn't look good when "original size" is not enabled (little blur, not sharp as original). Not linked to any plugin as Jetpack acceleration is off and worked fine before, and nothing changed. Will this issue be solved in the next update ? Thx