Do you want to describe the bug you mentioned in detail and write a guide on how to fix it? (I understand it, but it would be great if we could add it to the general guide in a more accessible way).
Added 6 minutes later
I currently have this problem: the inside of the guard's helmet is transparent on the face side. It's easy to fix, but it's not easy to describe how to fix it for a beginner. I'll think about it.
And in Heroes, is there a function to create a two-sided material? Does anyone know how such functions work from the engine's point of view – does it multiply the number of polygons calculated in the game or not? (This can be found out by cutting it directly during the game with some ripper and examining it in Max.) If the polygons are not multiplied, then it is more relevant to use this function; if they are multiplied, then it is more relevant to select only the necessary polygons and manually copy and flip them in Max.