So I am getting some sustained flames when cutting all of a sudden. Looking around this looks like it could be a clogged hose / a hose that needs to be cleaned?
I had that happen. I cleaned out my machine thoroughly, including the vent, and it went away. 
The air assist fan or the duct fan that goes outside?
Both. They were supper dusty and clogged.
I’ve had this happen and cleaned out the air assist and it corrected it. When you cut, your flame should be blowing to the front if the air assist is working at all…and, shouldn’t have much if any flame…
