This is the one area most people overlook when purchasing portable audio. What will you have to do in order to get repair service? It is one of the main reasons I am apprehensive buying Chinese DAP's. Cayin is kind of an unknown entity and I will be waiting to see how N3 buyers experience Cayin repair services. I have had very good experiences with Sony and Fiio regarding product repair/replacement and a total nightmare with Cowon.
Yeah, I've been burned before. A few times on audio products, and other times on other types of Chinese electronics (Mini PCs, tablets, charging cables, li-ion batteries, handheld gaming devices, kids toys, clothing, etc).
It's really a crapshoot. Often the seller offers a partial refund. Other times they expect you to ship it all the way back to China for service or refund (which the shipping costs alone often exceed the original cost of the item). And asking Aliexpress etc to step in and help doesn't always work out in your favor either.
In the cases where I'm looking to lose all of my money, I tend to settle for a partial refund (ie losing some money is better than losing it all). In other cases, I just eat it if it's just a few bucks. Or other times they are willing to reship the item.
If you use sites like Amazon and ebay, you pay more for the items up front, but you have the power of ebay or Amazon behind you. I had some $80 headphones that I got from Amazon recently, and they died after 3 days. I printed the return label right from the Amazon site and shipped them back for a full refund. Took 5 minutes, and was easy as pie. A similar thing happened to some IEMs I got from Aliexpress a few months ago, and I ended up losing all of my money because the seller wouldn't do anything, and Aliexpress basically told me I was SOL when I did a dispute. I spent hours of my time over the course of 2 weeks sending evidence videos, photos, and going back and forth with messages. I was going to them dispute it with my credit card company, but by that point it just wasn't worth my time over some $12 IEMs.
So basically you accept that you'll win some and lose some.