Term page: nodes grouped by multiple sub-terms

I have one vocabulary with hierarchical terms.
Term 1
--Term 1.1
--Term 1.2
Term 2
--Term 2.1

My nodes could be classified with several sub-terms from a same main term.

For example Node-1 could be tagged with Term 1.1 & Term 1.2 (but not with Term 2.1)

I would like to display on Term-1 page all nodes with Term 1.1 & term 1.2 group by sub-terms.

My view:

Path: taxonomy/term/%

Contextual filter: Content: Has taxonomy term ID (with depth)
Depth: 1

Fields:

Content: Rendered Node
Content: Product category (hidden)
Multiple field settings
Display all values in the same row -> Unchecked

Format: Grid
Grouping field: Content: Product category

It works great when i"m seeing a main level category
But goes wrong when I'm on a sub level.

If I have a node under term 1.1 and term 1.2, when I will see the term1.1 page for example, both sub-categories "term 1.1" and "Term 1.2" will be displayed (as group) instead of only Term1.1 because the grouping field is my node terms and not the one of my contextual filter.

Any help would be really appreciate...