I would disassemble everything, give it a thorough soap-water bath, lube up the o-rings and fit it all back. The feed holes, chimney shaft, under the deck could have juice/gunk/soot traces to give you that trouble.
Absolutely agree with this, especially if you've had it a while- I was getting terrible dry hits with my K4 a few months back- turned out a couple of the juice feed holes had got gunked up- after an ultrasonic bath it ran sweet as a nut...

