gear-related Blurry footage from my Canon 5d Mk IV?

I am having some issues with filming video on my Canon 5d MK IV. When using Full HD the footage looks really bad quality when I play it back - blurry and fuzzy. It is fine on 4k so the problem isn't the focussing. Is this expected or can I adjust some settings to make the video on full HD look a better quality?

Thanks in Advance.
I don't know that camera but you can look for a setting that allows you to adjust sharpening or image enhancement. I know some cameras only achieve really sharp images by enhancing them digitally inside the camera before saving them. Just like applying the 'sharpen' filter in Photoshop... on the other hand, if your video looks good in 4K but not in HD, that may not be the solution since I believe both formats, 4K and HD, would use the same capture settings..