Views contextual filters summary display nodes id instead of title

Question

I have a content type customers who has a required entity reference field to a content type groups. I have create a view to show all customers nodes and I have added a contextual filter over the entity reference field to display a summary of groups with a count of customers per group. The view uses fields, and I have added nid, title and reference field from the customers content type. It works good and if no group is in the argument, It shows the summary, but instead of display the titles of the group, It display the nid of the group.
Following this answer I have put the title when a group is selected, but the summary shows nids. What should I do to show this nodes titles?

Edited:if I do exactly the same with D7, it shows the titles as expected.

Answer 1

I have found how to do it. Firstly, I added the relation between customers and groups in the "relation" section. After this, instead of adding the relation field as contextual filter, I added the title field as contextual filter, but I checked the relation I have created. Then, when the argument is not present, It shows a list of groups (with their names) and the count of record.