I've only been vaping for about a month and am a total noob. I have the nautilus mini because it came in my starter kit, and in the first week I burnt 2 coils, and then had a major flooding incident. I was totally frustrated and and almost gave up. I then turned to YouTube and read and read and read, and like many others here, found that you cannot over tighten them. And the draw you take is imperative to the flooding issue. Being an ex smoker I was trying to vape like smoking a cig, and I was hitting it hard and pulling in more juice than it could vaporize, which flooded the coil. And because everyone said not to over tighten it, I didn't have it tight enough, and it started leaking out the bottom and one time I picked it up to use it and it was slimy from all the juice that leaked all over my battery (the iStick mini).
What I found, as far as tightening, is that you have to snug it as tight as it will go without needing pliers to undo it. In other words, don't crank it down, but don't leave it loose either. If you screw it on to your mod by the glass and it turns, it's too loose. Also check the silicone o-ring because I found that if it's screwed too tightly, when you undo it can pull it out slightly, which may lead to leaking. So now when I put back together after a refill, I just run my finger nail on it all the way around to make sure it's in place and good and snug. Takes 2 seconds.
And then with your draw, you want to go slow enough so that the juice you pull in actually vaporizes. Start on the smallest airflow hole till you get the hang of it. It might help prevent you from pulling too much juice. Especially if you're an ex-smoker, it's going to feel the most like smoking a cig on that hole. You may also be over priming it before you use it. Start on a low voltage with the tightest air hole, and draw slowly. Bump the voltage up and open the airflow slowly till you get the vapor and flavor you like. You shouldn't be coughing, and it shouldn't be gurgling.
Since figuring out these little nuances I haven't had any problems. No one gave me a lesson on how to vape when I bought it. I just took it home and hooked up and started puffing away and then had all these problems. It really is totally different than smoking.
I then bought the same starter kit for my father in law's wife who wants to get off the cigs, and she's having problems with flooding and hacks and coughs every time she takes a puff and refuses to use the thing half the time and insists hers is defective compared to mine. I've tried explaining till I'm blue in the face all the things I've learned, yet she tugs on it like she's pulling the last drag of her life, then coughs her brains out, then her next draw is nothing but gurgles. She then attempted to refill it without so much as reading the manual or watching any of the videos I linked her to, then put the thing in her pocket, it leaked everywhere and she had a juice stain on her pants all day at work, which made her hate the thing even more. LOL
I keep letting her try mine because she's having troubles finding an ADV that she likes, and she does the same thing to mine. Takes a power puff, than coughs her brains out, and then I have to spend several minutes burning off the excess juice till its vaping right again.
I hate to say it, but I'd vote either a fake, a crappy "refurbish", or user error. Between my husband and I we now have 4 nautilus mini's and we love them. Luckily the new vape store we found, which is awesome!, has their juices set up on different tanks so you can not only try the juices, but try different tanks, and flavor wise, not many come close to the nauty. I think a kayfun something or other was pretty good and I'm thinking of buying one simply so I have something to compare my nauty to, but I can totally relate to all the problems you're having because I had every single one in the beginning.
A good vape shop should be able to help you out if go in there and explain the problems you're having. They should take it all apart, show you how to clean it, get the excess juice out, put it back together, and then take the correct draw so you don't flood it again. Before you give up, I'd focus on finding a good shop that will let you try different tanks, and will help you with the one you have. While we were at the shop the other day there was a woman who came in that was having problems with the tank she just bought (not a nauty) and thought it was defective, and the guy took her over to table and they sat down and he helped her trouble shoot and they came to the conclusion that she was just sucking on it too hard. It seems to be common problem among noobie vapers who are ex smokers. We just assume that we should use it the same way as we smoke a cigarette, and that's not even close to how one should be vaping.
Don't give up!!! Try different tanks before you buy if you can, and find a good shop that is willing to help you instead of just trying to sell you something else. We are so lucky to have the shop we did, and turns out it's only 10 minutes from our house.