Often when we get blockages it can be down to plastic in the heatbreak , as this will not melt when the hot end heats up . This can happen especially if you are replacing filament by the pull method . We always prefer to cut filament just above the extruder feed , push the older filament down through the extruder when the hot end is heated with an old bit of abs , and then feed in the new filament and do some manual extrusion until the new filament comes through . This prevents pulling plastic into the heat block . But you need to find a method that you are happy with . As to PTFE , it ' s cheap enough , if it get damaged just replace it , having fresh ptfe is good anyway as it improves performance as over time you get more friction from it as it wears from use .