Probably the cracks aren't of any concern, as far as
water infiltration goes. If they are hairline cracks, you may
confirm this by throwing clean water on the crack.
It should soak in before it goes far. Bear in mind water
runs downhill, and the stucco has a vapor barrier like tarpaper behind it.
I do have a solution to re-coat your walls over in a manner where
the cracks will disappear. The doubt I have is the fact the lath may not
been overlapped enough( at least one inch). There is a possibility the
will come through.
What seems bad is the cracks are vertical, and probably the distance
apart as a sheet of lath is wide, or just over 2 feet.
Here is my solution, even though I have a little doubt it will
It sounds like sloppy work due to lack
of experience. There may be hope.