ZBrushCentral

Weird material shading when model is partially hidden

Does anybody experience the same issue with zb4? it seems like when I have part of my model hidden I will get these weird square shadings on my model, it looks like as if is another materials been applied on my model but I couldn’t get rid of it.

I had this problem to before, and i thought the problem is on my graphics.
Then i stop doing it and shifted to making another.