Russel & Gerry, There is a good chance it was a number of things.
1.They way it was flashed at the top.
2.The lack of fastners into the framing members/studs. And in between them.
3.They did not let the base coat shrink and crack out before they put the finish on, therefore when the shrinkage and cracking occured it was in the finish also. Leaving cracks in other parts of the wall to let water in.
4.Once the water got in every freeze and thaw cycle made it worse,finaly the lath rusted out then te severe curling started.
5.The plaster was thinner where the oversized laps in the paperback lath occured due to the way the product is made! tey had 2 layers of metal and paper. When you are putting lath and paper on it is important to have paper on paper and lath on lath. Also required by ASTM.
6.At the corners the moisture barrier was cut short letting more water in between the paper back lath and the foam that has a thin plastic film on it that is water tight compounding the freeze and thaw problems. When water gets in it does not always run down.
There is more then this but it is a start.