Did you take any of the stainless ones apart and remove the filler to see how they are made and what exactly the difference is between the stainless and the powdercoated? I'd sure like to know if there is any difference in filler density, filler material and coil placement.
Edit to add: I know that when I first started ordering the Chopper
tanks they came with gold-based cartos that didn't work very well, for very long. I took them apart and they were built using a totally different process with totally different materials. Coil was different. Filler material was different and not very uniform. They had a metal rod alongside the centertube. they didn't have the thin filler wrap at all, instead they had a hole punched through the centertube with a piece of filler stuffed in horizontially. Obviously these were not made by Kanger and if they were, Kanger made an attempt to modify the design to prevent people from rebuilding them. After disassembly, it was obvious that these were designed to be used once and not for very long either. Admittedly and to his credit, Chopper took the gold-based cartos out of circulation quickly and replaced them with what appears to be genuine Kanger cartos. Problem solved and Chopper's tanks are great now as far as I'm concerned.
Sometimes I think that some batches of cartos are like Chevys built after lunch on Fridays. They suffer with quality issues due to operator error. The principle is great but the actual execution is flawed depending on the assemblers of the day. I don't know the exact building process the good folks in China use for making them but I would guess that it's a combination of automated machinery and hand work. The problems I've noticed from reports on ECF is that the filler quantity is inconsistant. Too litle and you get flooding. Too much and the density doesn't allow for proper wicking and you get a burnt taste even with a full carto. sometimes the machine that inserts the filler doesn't press the filler package all the way to the bottom and sometimes the cotton centerwrap is initially positioned too high to wick
juice consistantly to the coil. All these problems can be rectified by using the rebuild method and having a good comprehension of how these units actually work. I have not experienced many of these problems with different batches of cartos as I am still using original cartos both in stainless and black paper wrapped from March of this year. I bought in quantity at that time and in all honesty, the rebuild method works very well for me. I've been using the gogo daily as my main vape since early March and I've only had to throw away 7 cartos over that period of time, all for burned out coils.
So here's what I'd do in your situation. I'd disassemble the bad stainless ones and check to see if it is a genuine Kanger. Compare filler size and density with the good powdercoated ones. I've noticed different amounts of filler when I've taken out 10 or so for cleaning and rebuilding all at once.
If it's a genuine Kanger that you can dry burn and refresh the coil then repack it with some filler you know is the right size from a carto you had real good luck with and are waiting to clean and rebuild. Note: I always save my fillers from cartos that have burned out the coil. Also you can repack the suspect carto with Fluval. Just make sure you use the cotton wrap with it. Fluval is less dense and I cut it 1/3rd wider and 1/3rd longer than the original filler on a good carto. (After splitting the fluval pad lengthwise into thirds)
I'll be very interested to hear the results of the teardown and what you find in the way of materials. I know it's a pain but gogo nation has a track record of finding answers and solutions for any glitches that appear in the system.
