Help remove non-existent variations of the goods that have become duplicates of

I found out the following problem on my website:
When you add an accompanying product, namely an apseal, one of the added goods has variations (being a simple commodity). This situation is most likely due to the fact that when I created this product I copied a similar variant product and made it simple.

I was wondering what would happen if I add one of the variations as an apseal and click on it. Clicking on the added variation of the product, I redirected to the parent product.

I decided that fixing the problem would be helped by re-creating the attribute of the product, which is used for variation. I deleted this attribute and created it again.
To make sure that the problem is solved I go to the editor of any other product and try to add a problem product as an apseal. I see that now the problem has a slightly different look). Now instead of variations of the goods 11 identical simple goods are displayed. If I’m not mistaken, then I need to clean the database.

The screenshot shows that adding the apseal, the same product is repeated in the list.
link to screenshot: http://ipic.su/img/img7/fs/Snimokekrana2018-03-20v10.1521538197.png

How can I delete an existing duplicate from a particular product?