I must have old twine. After I re-knotted it, it would just pull apart. Or I have a cheap grade of twine. This hasn't happened to me before either and I think I have the cable set up for about 3 or 4 years. My Sterlings came down a few more times, so I just picked them. They were ready early this year. The others will hopefully stay up until they are ready to harvest.
I did tighten the twine once this year. But not totally tight. There was probably still a foot of slack after I tightened the twine.