Either your wick is drying out, or there is a short somewhere. Or both!
Follow sumoman's instructions on getting the coils glowing evenly, then see if the problem persists to any degree. If you still have dry hits/burning then the wick is just drying out.
It's hard to tell from the pic, but do you have all the deck holes plugged? Take a screw out somewhere (if you haven't already) so you have an air hole in the deck. This will allow the juice to wick much easier and reduce the chance of drying your wick out.
Also, gennys usually need at least a little bit of a tilt to function properly, known as the "genny-tilt" When taking a puff make sure the wick is on the bottom, and the device is tilted a bit. This will also help juice feed the wick. When doing cap-off juice burns tilt too, with the wick on the bottom.
There are people out there claiming perfect vertical wicking, and/or good feeding with all holes plugged, while they may be lucky for most people you need to leave a hole open and tilt a bit.