I have several rolls of 1.75mm filament which previously had fed fine. After doing a major salvage operation after my last disaster, I hooked up a new heat sink to my existing hotend. I couldn't figure out why it wasn't feeding until I disassembled the thing. Filament will go through the heat sink with no issue. However, it won't go through the heat break. There was crap jammed in the heat break and I got it out. However, the heat break has too small an internal diameter to pass the filament. I looked at it very closely and if it's deformed it was symmetrically deformed, so I doubt that is it. Is the filament supposed to go through the canal in the heat break? Or is the heat break supposed to get hot and the plastic start melting in the middle of the heat sink? And yes, it's a 1.75mm heat break and 1.75mm filament. A 0.4mm spare nozzle I have snuggly passes the filament up to the nozzle head.