these cracks are now acting like expansion joints in the sidewalk. these occur around windows and doors where studs have been removed and its the weakest part of the house. Anyway, no need to work too hard on making them go away because its futile. Apply some latex paintable caulk in the crack and force or cram it deep into the crack. This will allow some movement before it cracks again, and can be painted over.
Anything that does not have latex in the product will crack.