According to RJ angreal and sa'angreal were being mass produced during the War of Power much like tanks, airplanes and other much needed equipment were being mass produced during WW2. But as the War grew longer, the industrial capacity of the world was diminshed as society started disintegrating. As mentioned in other quotes, by the last years of the War armies had reverted from using shocklances to using sword and bows and arrows, simply because the capacity to maintain a technological infrastructure base was diminshed and eventually virtually destroyed.

Now, as far as Callandor was concerned, RJ said that due to the above situation and the speed at which these angreal and sa'angreal were being manufactured by necessity, the rate of technical faults in completed products increased. And Callandor was one such case. So disappointingly, it wasn't a special case, or the result of deliberate sabotage or interference by the Shadow. It was simply a faulty product on the production line. One of many where something went wrong.

And yes, my first thought when I read that was: "How the hell did they build the Choedan Kal, right at the end of the War, if something of that strength could not have been developed at the height of their technological capability.

But I guess it is similar to the Atom Bomb. The Manhatten Project, which was completed close to the end of World War 2. And Germany were only a few years from developing their own Bomb, despite the destruction of much of their infrastructure. And of course, it meets RJ's plot requirements, just like so many other unlikely occurrences in this series.