Good morning,
I have some problems with the import of products via CSV. 
The suppliers are already added to the system, also via CSV, at the contacts page and everything is set-up correctly (in my opinion).

Now I would like to link those suppliers to the products via the seller_ids, but whatever I try, I can't make the link. 
The ID's I could find of the suppliers are like this: __export__.res_partner_277 , and this is also what I filled in at the seller_ids. 

If I validate the CSV I get the following warnings:

• warning -- AccessError One of the records you are trying to modify has already been deleted (Document type: Information about a product supplier).

Or sometimes a nonegroup warning. 

Is there something I do wrong or is it simply a bug?

Thanks!