[Help me Please!]Map Bug

Hello !
I have a problem (Serious problem for me) !
I'm a mapper and I've mapped a place but i'm getting a serious bug.
The current bug is Appearing and Disappearing !
Sometimes when I try to get close from an object It will appear and sometimes and when I get far from there it will disappear!
Please anyone can help me?
Pictures:
http://imgur.com/a/ROtx1
~Thanks