For repair of a continuous loop I really liked Fayetteville Snob's answer, but modified it slightly. Snob said "The cord welds together with heat. Light the ends - extinguish and quickly join together while still hot - roll the weld with fingers - let cool." I melted both ends with a lighter, stuck them together (I had to do this a couple of times to get it right), then trimmed the excess melt so that the cord would go thru the roller. This didn't look like it would hold for long, so after the trimming, I wrapped it tightly with dental floss! Worked perfectly and, much to my amazement, it still working after a couple of dozen cycles.
Rick's Fix, June 2017