I had the same problem, it was because it is summer and I am in the garage at around 100 degrees F. I fixed it by pointing a floor fan into the printer and the prints finish now.
The thermal break tube did you replace it when you changed the nozzle? some times incorrect installation wear on the PTFE lining or using one that doesn’t have a thermal break in the threads has ptfe tube through the whole throat of the tube, or no ptfe in the tube at all will cause symptoms like you are describing.
I am using this one it has a partial ptfe lining and the thermal break in the threads, it has a tapered inside diameter on the filament inlet side too.
My Replicator 2X is 7 month old. It is a replacement by Makerbot for the broken one I had previously. Both printers have the same Mk7 extruder with the spring lever.
when was the last time you cleaned the feeder ? sometimes the filament can grind and leave residue in the teeth. This caused the motor to slip on the filament and grind your filament.
This list is pretty complete. The only thing I would add is to check the spool to check if the filament is not tangled. When you remove a spool, sometimes you let go of the tip of the filament and it unwinds a bit. It happened to me once that I just grabbed the tip and pulled it to tighten the loose loops around the spool. As it turns out, what I did was basically tied a knot. When I tried printing again, it printed fine until the knot tightened to the point that the spool would not turn any more.
Also, when the spool is on the last 10-15%, it seems it is harder for the extruder to pull the filament. Lubrication on the spool’s bracket helps. A dry lubricant, like graphite works nicely.
What material are you using? Always happen to the same height and with the same piece?
Once I was printing a piece in abs and at certain height the impression was suspended; The strange thing is that it always happened at the same height.
After trying everything, I realized that the piece had a thin wall at that point and due to the machine trying to make it, it performed constantly retractions that ending up on a bearing eating the filament.
Try several things:
1. Suspend retractions. The piece might look terrible but you will try if that is the problem.
2. slow the print speed or increase the minimum duration of the layer, in the Makerbot software
3.If it is a mechanical problem, adjust the bearing pressure
4. In this link Print Quality Guide | Simplify3D Software 129, check the “Stops Extruding Mid Print” information, you might find it usefull