These fields appear only when submitting the file. Anyway, that's my category settings:
So for the video below, I don't even use the UPLOAD field in the file category.
I uploaded a new version, changed nothing, and hit save. After a hard-refresh, the category image is gone:
I disabled the Save Previous Version? option but it doesn't make any difference.
The next step is to upload a new version and remove all screenshots. Save. Upload a new version with the screenshots.