Error in rebuilding the Equation

Hi,

I am having a problem in Equations of a part.

Firstly I used equations for some hole dimensions with in the part level only. And then I controlled the external dimensions with reference to another part within the assembly. There  was no error and was working perfectly.

When I closed and reopened that assembly it is showing error in equations in a all the parts where equations are used. When I opened the part and manage equations and rebuild it the error disappears. I even tried to select the option automatic rebuild but it doesn't work.

Is there any other way to resolve this issue

Thanks in advance.

SolidworksAssemblies