I had a similar problem in the past when I unknowingly stripped out a hub; it seemed to seat properly but one day when I tried to skid it loosened up and almost threw me over the bars.

I would stick with EAI or Shimano Dura Ace cogs/lockrings. They don't cost that much more than the budget cogs/lockrings and you get way better quality. It's especially vital that you stick with a high quality cog/lockring combo if you're running brakeless. An extra $20 or $30 isn't worth slamming into the side of a car.

I personally run a Dura Ace 16t cog and lockring and haven't had any issues as of yet nor do I expect to any time in the future. Plus, it's way more fun knowing you have the confidence of a quality drivetrain!