Hello again, seems like I always stumble upon problems
So I took a screenshot, let me show you:
On the left side, I merged a wall_door_way_arched with a Wall_Default_Short, but when I'm in-game it doesn't seem to fit that well.
On the right side, I used Wall_Window_Blue_1 and merged it with Wall_Default and you can easily see the white "bug" line showing on the screenshot. And this screenshot makes it look better than it actually is.
What am I doing wrong? How can I make them fit better together?