Wall Line Disappearing

[builtra]

i have an existing wall where i am adding doors / windows too... for some reason at some point the walls have the lines disappear... the wall is still there and sometimes i can reverse sides to get it back but now i cant just reverse the sides

any help appreciated  

[builtra]

i found the way to get it back... i use wall types so i changed my type to a wall with same thickness and then changed it back