products added to category not saved

Question

Catalog > Manage Categories

I select a category and go to "Category Products" tab. I reset filters and select one or more product to add to category. Then hit "Save Category" button and the category is indeed saved but the products have not been added to the category.

If I remove a product from a category then it is saved and removed correctly.

I have tested with new and different categories and the problem is the same. I have cleared caches, checked logs and there are no errors neither exceptions, no js errors as well.

Any possible idea would be appreciated.

Answer 1

final update:

I actually solved the problem after some heavy debugging

The problem was caused after hiding "Position" column on grid by using an extension.

As it turns out, Magento checks for the existence of position input field, which is included in "Position" grid column, before saving a Category Product. If the position input does not exist, it ignores the product.

The same check is not happening when removing a product from Category.

Hope to save someone's time in case anyone else runs up this problem.