TAZ 6 randomly stops extruding

The printer had been running perfectly for a number of years and suddenly began grinding the filament but not extruding. Bought a new extruder and have the same issue. Upgraded to CURA 3.6.31 and Merlin, nothing helped. If I monitor the printer closely when this happens, I can physically reduce the pressure on the print head and push the filament by hand and it will start printing again. It acts like the nozzle temp is dropping but there is no indication on the display. This happens regardless of printing temp.- 195c to 230c. Using PLA+. Contemplating a new RAMBo board. This one is V1.3 and the new one is V1.4, will that cause more trouble? The current print project takes from 5 to 8 hours depending on high speed or standard printing speed.

I had that happen with a Taz6. I finally traced the problem to excess backlash in the driver herringbone gear. When doing a print with lots of retraction in one spot, the wear due to retraction and feeding backlash would chip away at the feeding filament. I used nylon to print a new drive gear, keep it greased, and had no more trouble.

I had this problem. Turns out the fan on the heatsink had shut down and the tube leading to the extruder was melting the filament and it jammed in that tube.

Have this problem quite often and my remedy is always cleaning the nozzle with a lighter and sharp instruments.

This was a lengthy project that is finally over and I’m not sure the problem was definitively resolved but if I had to guess, it likely had something to do with 1. Operator error or - 2. As suggested earlier, there were multiple retractions in a couple areas that could have damaged the filament to the point of failure. The up-side to this is that I learned a great deal more about the machine. Thanks