Problem importing combinations in multistore

[girtri]

Hi I'm trying to use multistore in Prestashop 1.7.6.3 (Php version is 7.2.24).
I have installed prestashop normally with samples data, then clear data and activated multistore.
Then I added new shop called shop2 (virtual url shop2).

Now I do this things, trying to import data from csv:
1) import brands from csv with "All shops" selected: everything ok.
2) import categories from csv with "All shops" selected: everything ok.

3) import products with field "id_name_of_shop" set correctly: note that csv files contains the products of both stores.
If I try to import with "All shops" selected I get an error (generic error without details).
If I try to import with "Default group" I get an error.
If I try to import with the first (main) shop selected everything seems to be working properly:
products are loaded with the correct association with their shop. In fact, if I go on catalog and change selected shop I see the correct products listed (filtered by shop).

4) Now my problem trying import combinations (with field "id_name_of_shop" correctly set): note that csv file contains the combinations of both stores.
If I try to import with "All shops" I get an error.
If I try to import with "Default group" I get an error.
Then I think it could work like importing products, I select the main shop and import csv but this procedure does not work properly!
After importing combinations, a product with combinations of the second shop (not the main where I imported) loses information about the category and also other data (like id tax rules!).
I verified this querying the "ps_product" table on database where I can see the field "id_category_default" with zero value (before import combinations it was correctly valued).

Can anyone help me understand where is the problem and what I'm doing wrong?
Thank you in advance.

[Ricky05]

I have the same problem with importing combinations, have you solved the problem?

[girtri]

No I haven't solved it anymore