I'm not really very good with a torch, but have a few ideas and
suggestions which might help.
A few questions first:
Are you using a carborizing or oxygen rich flame?
Are the tips you are using meticulously clean? That includes
using a tip cleaning tool and/or possibly removing the tip being
used and cleaning it in an ultrasonic cleaner.
Have you tried using different types of fluxes or soldering
Is the tip size appropriate for the type of material(s), energy
sources and temperature needed?
Two causes come readily to mind. Firstly, the flux is bubbling and
causing clogging of the torch tip. Secondly, the torch tip is so
large that the materials being heated are literally being dislodged
and flying up to clog your tip.
Another two possibilities:
One or more of the line fittings between the tanks and the torch are
not adequately tight.
The torch body and/or the regulators need to be repaired / rebuilt /
Being self-taught in the use of a torch I've had to learn through my
mistakes, and generally found I was using the wrong setup/equipment
or needed to improve my torch techniques.
Sorry I couldn't be of more help. Just remember using a torch
involves many variables. When something works be sure to remember
or record the setup and what you were doing. When all else fails,
try going back to something that previously worked
Wishing you the best.