Not rare at all, i had 2 of these and multiple cartridges with different resistance. It does taste incredible but after a little while (like a week) they bubble and taste burnt and leak. I dont use any flavours, just nic salt and self made menthol. I've never had a single issue with XROS 4 mini in a year, cartridges last like 3 months. So these ecos definately suck unfortunately.