Colt made a mistake in lighting the frame(that oval cut you see in the rail) which caused binding of the spring, thus the slide beat the frame to death.
I wouldn't say Colt "made a mistake." The slide and recoil spring designs were the same that Colt had used for many years succesfully.
The MARSOC tests were designed to test the pistols to failure, which they did after many many thousands of rounds with little or no lubrication, and with the guns filled with sand, dirt, and other debris.
The end result was to take an excellent pistol design and make it even better.