I've been trying to fix up an old Makerfarm Prusa i3v that I abandoned a few years ago for a similar issue with constant jamming. I've used my Original Prusa i3 MK2S to print off a new extruder block as well as some other pieces. The extruder block works flawlessly. The problem I'm having seems to be from the E3D-v6 hotend. When I assembled it for the first time, following the assembly instructions to the tee, I applied even thermal compound across the heat break's top part. I pushed the PTFE tubing as far as it would possible go. I even unscrewed the heatsink from the heatbreak to ensure visually that the tubing was seated in the heatbreak. I performed the final heatup to tighten the nozzle. When I hooked it up and used Pronterface to test some extrusion, the first strings came out fantastic. Five seconds later, upon requesting another 10mm extrusion, the filament can't move and the drive gear is now digging into the plastic. I couldn't get it to extrude manually even with substantial force. I disassembled the hotened and found plastic built up in the base of the heatbreak's upper component, as if it pushed the tubing out, hardened, and blocked it. I managed to get it all out by heating a paper clip, stabbing it into the plastic, letting it cool, and pulling it out. With the heatbreak cleared I performed all of E3D's assembly instructions as stated above, ran an extrusion test and get perfect little strings the first time. Five seconds pass, request another extrusion, and the unit is again blocked. Any ideas? It's quite frustrating.