It is possible that the nozzle is just worn out but I didn't ever use a drill bit to clear the nozzle. My technique was to remove the nozzle, heat the block, then use a 1/16 drill bit gently in the teflon tube. I did that several times and it worked well but one time I got a little too enthusiastic and pushed the drill bit through the side of the teflon tube. I then ordered some 3 mm OD, 2mm ID PTFE tubing on Ebay. It turned out to be slightly more than 3 mm in OD but I managed to get it in the block and get the nozzle back on. Just today I removed the nozzle to inspect and found that the PTFE tubing is burned and broken. That may be the cause of my problems. I don't know why it burned unless it was not PTFE or that PTFE is not the right material. Now I am kind of stuck. I think I can clean out the block but I don't have a tube to replace the original and apparently don't know where to find one. I have tried to contact CTC to see if I can buy any parts from them but they haven't replied.