URGENT! Products Dropping Categories

-- url of the page with the problem -- : shop.justducks.co.uk
-- HikaShop version -- : 3.0.0 BUSINESS
-- Joomla version -- : 3.6.5
-- PHP version -- : 5.6.3
-- Browser(s) name and version -- : all

When performing minor product changes, such as text or price, and the product is assigned to multiple categories, the product is dropping the categories into which it is assigned and the database shows it is only in a category ID=0, which appears to be the root.

This is a troublesome situation.

Please advise as to what might be the cause of the categories dropping when a product is modified and saved.

We have found the issue and resolved it.

For some reason or other, products were being assigned directly to the root category, re: Category ID 0.

There were about 15 such occurrences out of 925 products.

We checked the product-category table in the database and discovered that category assignment for some products.

The root category assignment was manually removed on the product admin screen.