How to display block with term image field when viewing term node
I found my error: In the Format: Settings I had Grouping field N1 selected with the category term image field, which caused the duplication of the image.

Contextual Filters: Content has taxonomy term ID (with depth), Depth:0, Provide Default Value: Taxonomy term ID from URL > Load default filter from term page
Relationships: Entity Reference: VocabularyName - Require this relationship
Fields: Taxonomy Term - the term image field - using Views Distinct I select Filter Repeats