Hello. Probably many of you had this issue. Sometimes after creating a separate surface inside a wall the new color without breaking through and many times it creates a ugly mixture of surfaces. Why is that. What is the rule here and what tools to use instead of pushing or pulling the wall or surfaces? Why sometimes it works as it should be and another time its such a problem?
This is called z-fighting and happens when two faces try to occupy the same place. SU can’t display both at the same time so they flicker as you move the view.
As Box said, there are two surfaces one on top of another and that is is the reason for this to happen.
If you use a model with a single plane then move it from that wall few mm, and if you do not need that surface on your model, that shelf i.e., then delete that surface on that shelf.