Just a guess Nick, uneven fuel atomization. Maybe a broken needle.

If a lot of liquid state fuel gets into the turbine during operation, the swirl seems to kick the "liquid fuel" hotspot up to maybe 4-5 o'clock position, looking at the rear. I have rarely seen the bottom (true 6 o'clock) of the nozzle get that hot. My money is broken needle or some sort of leak in the fuel manifold.