My guess is USER ERROR, especially since it appears you've had issues with flooding and spitback with other devices (?).
I don't have your device, so I researched it on You Tube.
Are you careful to only fill it to the max fill line?
Are you using too strong of a draw technique? Try using a soft, gentle draw, especially with a MTL tank.
Flooding and/or "spitback" is a common occurrence in e-cigarettes. The definition of flooding is getting juice into the air passage of the tank. This can include any point between the mouth piece and the very bottom part that connects to the battery. Each tank has holes in that air passage, where the wick passes through. This is required for the device to work properly. Unfortunately, this opens up the possibility for flooding. The trick with flooding, is knowing how to avoid it. A few common causes for flooding a tank include: improper filling, over filling, pulling too hard when hitting the device, and the temperature can even play a role and/or damage.
Improper Filling: When filling your tank, you have to be careful not to get juice into the center tube of the tank. This center tube is the air passage. When you take a draw, air comes from the bottom of the tank, through the air passage and into your mouth. If you get juice into this passage way, your tank is flooded.
Over Filling: If you over fill a tank (specifically a top coil like the ones that come with the starter kits and gift boxes), the wicks can become over saturated and just like a rain cloud, they will leak into the air passage. Once this happens, you have a flooded tank. Don't over fill!
Pulling Too Hard: Probably the most common culprit to flooding and spitback. As I mentioned the wicks absorb the juice in the tank. As you pull on the device, you cause a vacuum effect that pulls juice into the wicks. If you pull too hard, you can pull in more juice then the coil can vaporize. If this happens, the juice leaks into the air passage and you have a flooded tank. Use a softer, gentler draw technique.
Temperature: E-Juice is a viscous liquid. Which means that as it warms up, it will thin out. And in the opposite form, it will thicken when it gets cold. When it thins, it is more difficult for the wicks to hold back the thin juice. This usually causes the wicks to over saturate and, you guessed it, it will leak into the air passage and you have a flooded tank. Don't leave your device in a hot car or in direct sun.
Damage: There are o-rings and gaskets used that can wear out with usage. If certain ones fail or get lost, leaking will occur, in turn flooding the air passage and causing you to have a flooded tank. Other than accidentally losing something, damage can occur when its carried in a purse or a pocket or by over tightening the tank to the battery. Over tightening is a very common cause of leaking due to the damage it creates. Never over-tighten anything, only "snug".
Having said all that, I will say that I'm not a fan of the one piece all-in-one devices as they seem to have more issues than separate tank and mod setups.
If you continue to have flooding or spit back issues even after using a softer gentler draw, perhaps you need to switch to a MTL (mouth-to-lung) vaping setup.
