Problem sorting products in category

[Andrea_17]

Hi guys, I find myself with a rather strange problem in ordering products within categories. In practice in shop> products parameters, I selected "default order = position in the category" and "default order method = increasing". So far everything is ok, but then when I go to choose the position of the products in the categories (with the reorder method), after a while they return to the original positions. I can't understand why. The only strange thing I noticed is that some products occupy the same position (screen attached). What could be causing this error? Has it ever happened to anyone? Thank you for your attention and for any suggestions or help.