It seems to be the old, disgusting story....the quality of the spare parts....
Indeed some years ago we all had problems with cartos until Boge seemed to have good quality, cartotank appears for all vapers and all pockets until....the carto disappears because in a pocket of five some were falls....
And until the Nautilus BVC it seemed to be the regue of producs from phantoms to others....RBA tanks a lot.
But nowaday we have some really well made products expl. Vaporesso target (but the c cells in my experience are very different in duration and flavour....), Vengeance mini, Ego AIO and now this Nautilus X.
I hope furterly that the same quality problems of the past in cheap chinese products don't repeat, a C-Cell is a very good one if well made, like Cubis replacement coils, Vengeance replacement coils, and many more including Nautilus X.
In My experience only the about 15 replacement coils of nautilus 1,6-1,8-Ni were good for the price and the quality, no one burned easily and die instantly...All the rest of the things is a Bingo you can win or not....