visual studio - Broken references in solution -

i have large solution many project. have 6 developers working on solution using vs2013 , source controlled tfs 2013.

periodically project references , file references dlls broken. little yellow sign black exclamation point shows next reference in project references , when @ properties of broken references, noticed path empty elements broken. remove , re-add references, have done few times before , keeps breaking again.

i googled around , found several people talking similar issues, in cases see, after removing , adding references, ok. case, keeps happening on , over.

is there known cause this? can keep re-fixing this, it's workaround , not solution.

assuming projectfirst generates dlls projectsecond, narrow down issue, can first build projectfirst , build projectsecond see whether behavior correct. if works, need check build order.

in solution explorer, select project or select solution. on project menu, choose project build order check build order. on dependencies tab, select projectsecond project drop-down menu. in depends on field, select check box of projectfirst must build before project does.

additionally, check projectsecond see whether default targeting .net client profile. if is, change regular .net.