Wrong "product code" = auto edited

-- HikaShop version -- : 3.0.1
-- Joomla version -- : 3.6.5
-- PHP version -- : 5.6

For convenience I don't add new products starting from zero, but I add new product by copying some of those that I have already created and then edit all fields.
Although I add the correct product code (e.g., SKU 12345), hikashop adds always the final numbers, e.g. SKU 12345_13 but there is no trace in the product page.

For each Item I copy and rename the title, product code and content, I get always the new product code with an additional number eg. SKU 12345_13

It seems there is no way to solve.

But I said I copy the item but then I always change "Product number" and I found however the final code added by Hikashop

I change the product code to: SKU 123667
Once I published the new item I see "product code: SKU 123667_13

But in backend I don't see any _13

I will try to be as clear as possible but I think it is a bug.

product added
Shoes1
Title: Shoes White
Product code: SKU 2234
Alias: Shoes White SKU 2234

Instead of creating a new product from zero, usually I copy one product already added and the I edit it:

1. Copy:

I displayed:

Item: Shoes1_copy

2. Editing

I make the following change:

Shoes2
Title: Shoes Red
Product code: SKU 2235
Alias Shoes White SKU 2235

Finally, I save the change.

In product listing menu I see the right Title and the right alias but on the front-end I displayed SKU 2235_13
("_xx" Where xx is a number)


I tried to edit again the product code = in backend, all fine but in front_end I get always the product code with a _XX (x x is a number)

I found the matter.
The code added at the end of product number it took from the "variants". Each variants as an auto product code (if not assigned)