“Automatic” isn’t really a video format. It’s a setting you allow Shotcut to set the video mode based upon the first file you import.
To see the true video mode/properties: Click on Master, then Properties.
What Video Mode properties do you have? (Resolution/FPS)
The same MLT, MP4, JPG, PNG, other?
What are the properties of the one you used on your current project?
Can you share a screenshot of what’s blurry? Including the whole timeline, and any filters used on the clip(s) in that section that’s blurry.