Touring in France last year on fixed I noticed a ticking sound from the transmission and discovered one side plate had split across the pin. I rode around 50k to a cycle shop to purchase a split link to replace the broken link. I've since done a lot of riding on that same chain, including a couple of 600s, and it's fine. I presume it was a manufacturing fault as it was nearly new and had only been shortened and fitted with a split link (of which it now has two).