HoMM3 HD is a mod (add-on) for the game Heroes of Might and Magic 3.

I tried running the game in 16-bit mode, and the result is this.

There have always been 4 windows in the artifact merchant.

That's precisely because there were originally four slots. Since they added one, it would be nice to reflect this in the merchant's window.

As I can see, the flickering is a problem only for me. But the situation with the slots is very annoying; personally, I constantly have to switch between windows because I visit the merchant often.