Sounds like you overfilled, or you had a drop of juice in the battery connection or on the top of the battery. Anytime a carto stops producing as much vapor check things in this order.
1. Is carto filled.
2. Is battery charged (in my experience, the last couple of puffs don't produce much vapor
3. Unscrew carto and wipe both connections with a tissue or Qtip to get juice and condensation out (this is almost always the cause if the answer to 1&2 is yes)
4. Clean the battery and carto connections like steeljan demonstrates
Personally, I don't clean the cartos at all, other than cleaning the connection. I dont switch Flavors in cartos though since the old flavor will always linger. The few exceptions would be if I go from mint to mint or fruit to fruit and I don't mind mixing them. By the second refill the first flavor is usually gone. I only do this if I'm not going to go back to the original flavor. For example, I want a fan of the cherry from my sampler pack, so when it was empty, I refilled with chocolate. If you have a flavor and don't like it, you can try a reverse tayrn soon to get out the juice in there and then refill with a different juice, but again, you will get crossover on the first fill or two.
On a side note, unless you are using very high percentage vg juice, your cartos should last. I have been using the same 5 cartos for a month now and they are still going strong. Each on has been refilled at least 15 times.
