Bob, do you mean the string for your ACS? If you do, I know the guy that makes those strings, and he's good--real good. There's a few things I can think of that might have been the problem:

The most obvious--he could have just goofed--I know I've had my share.

Strand count--did the original string have less strands than the one I sent? That's one reason I don't like tiny strings--they stretch more, especially on heavier draw weights and/or longer draw lengths.

String material/wax--it could have been a difference in material. BCY has been great to me, and I don't think that would be it, but it could be that he got some material that wasn't up to specs.; or he have have used a different type wax and/or had more wax in the string. Some folks think wax is what holds a flemish string together. Actually it's just the opposite--the wax is a lubricant.

Pre-stretch--I pre-stretch all my strings on a jig I helped make. I figure I'm putting at least 200# of torque on them. It doesn't get all the slack out (obviously), but it generally takes a lot fewer shots to get it settled in.

That's all I can come up with at the moment. And it might not be any of these. If it had been just anyone that made the string, my first guess would be that they just didn't know a few of the tricks to making a string, but I know the guy that makes the strings for O.L. is very good.