Here is something I learned, after many issues:

Broken mates can be prevented by "naming faces".

Right click a face, Go to "Face Properties", and give the face aname.

This is usefull on different part that have simular features.

For example, if I want to have a part concentric, replace that partwith another, it is possible to do this without losing mates

See attached.

Hope this helps someoneSolidworksAssemblies