After 4 months, the right channel of my C3's started dropping out, and one day I couldn't hear anything at all. There was no damage at all on the cables, as I handle these very carefully and store them in case after each use.
The sound in the right channel sometimes comes back if I move the cable near the plug though. So I would say that either the plug or the internal cabling in that area has failed. Either way, very disappointing for a $300 IEM. The good news is that I returned them to the store where I got them, and they would be sending them to the local distributor to be fixed or replaced. Updates to follow.
By comparison, my Yuin PK2's have been exceptionally tough and durable. I've yanked the cable on them pretty hard about 5 times and had them for more than a year, and they still work perfectly.