Why might not display products in OpenCart categories?

Question

opencart

Good day everyone!
I asked myself a question that has been bothering me for a long time - it happens that I go to my site, into any category, and instead of seeing the usual showcase full of products in it, I see a big bold inscription "Products not found, try changing the search conditions" (as if the category is empty). By refreshing the page through F5, nothing changes, but if you go back to the same category, for example, through the menu, then the category is "repaired" and shows all the products in it.
With what it can be connected? Where to look? What to dig?
OpenCart Version 2.2.0.0 (rs.1)
I didn't find any reason for this error. She appears suddenly and out of nowhere. It seems like from the "first run" within one browser session, but then I tried to "repeat" the situation - it did not arise .. You work, you work on the site - everything is OK, such an error does not appear. Then you go from another laptop, for example, through the main menu of the site - oh, it shows no products again, you go to the same category through the same menu (repeating to the same page) - there are products .. Some kind of mysticism. .

Answer 1

In the category controller, log the main variables and data received from the models.
So you will understand where the error is. Then it will be possible to think how to solve it.