in-context assembly problem

Hi,

I'm new to top-down design, I've downloaded this assembly file, but I have this problem: when I open the reference sketches (master sketches) in the assembly, even if I don't make any changes, when closing the master sketch, I get rebuild errors. Can anyone please help me?

From my understanding in-context modeling using this method is complex but can save time later if you want to change some parameter. Are there other ways to do such design using different method?

I've attached the assembly file, it's originally belong to this topic:

Thanks

Vahid

SolidworksAssemblies