Bowslinger, how the string is made will have as much or more to do with it as the material.
Short answer, that is very unusual for Dynaflight. I haven't kept up with how many pounds of the stuff I've gone through. I have gotten one or two "bad" 1/4# spools over the years, but other than that nothing like what you experienced.
For what it's worth, if 16 strands of Dynaflight '97 didn't hold up, 18 wouldn't have been any better. It was either some bad material, poor workmanship, or both.
Did you contact the stringmaker about the problem? I know if it was me I'd want a chance to take care of it.
Chad