I find that the usual suspect with these is wicking.
I use my couple protanks off and on for a spell and usually put it down when i get tired of the wicking problems. They have a VERY sensitive line between flood and dry.
The normal setup has the center wick inside the coil and 2 additional bundles. This usually burns easy peasy. Removing 1 can be ok, but its easier to flood, and can still be dry, removing both usually floods the crap out of it and I just get juice puddles.
Note that the juice plays a huge role in this as well. Thicker juice, use less wick. Thinner juice, more wick. Finding that sweet spot is hard.
Not to be a downer, but this is what I think is likely going on for you. I really want to like the protank/bottom coils, but they are just so darn finnicky!
Straight up ease of use and drop it in and forget it, I go with a regular old carto tank anyday. Its just easier, and 95% of the time problem free.
Tanks run all over the spectrum, some from my experience:
Phiniac Rugged Pyrex Glass Tanks great quality tanks, 'pricey' but worth the quality
Odyssey Tank Beautiful tank, but a bit difficult to read levels, but great craftsmanship and warranty.
Then you have run of the mill cheap-er tanks
Ala:
Smok Tech Pyrex DCT works, nothing fancy, kinda need smok-tek pre-punched cartos tho.
YMMV but if you get a nice tank, it will last, just work, and something you will go back to time and again. Cartomizers arent hard to deal with, punching your own is pretty easy and theres a lot of tools out there to do it, or you can buy pre-punched.