Red lines when resizing ScrollBar

Hello,
I got a problem. When I resize the default ScrollBar, I get red lines.

When you start the game, they have everything works fine. But it makes me sick to see it on scene.
Can you tell me how to fix this?
Thank you in advance

 

It's probably the "scrolling area" or the "handle" game object. It's best to recreate it separately and then link it to the ScrollRect, after which to make sure you set up the anchors correctly (try to resize it in edit mode and see what causes the lines). Only then go and resize it to whatever is your requirement