I was printing a 45 minute project using PLA, temp set for 210c nozzle and 60c heatbed. At about 35% of the way into the print, the nozzle temp started to drop, going all the way down to below 190c, then the print job aborted with a message of "Thermal Runaway". I restarted the print, and it did the same. A third time, I watched the temp and when it got down to 190c, I paused the print, allowing the nozzle to cool down. I resumed the print, and the temp came up to about 208c, then started to drop. Again, at 190c, I paused the print and let the nozzle cool down. When I resumed, It stayed at 190 for about 10 minutes, then slowly climbed back up to 208c to 210c, for the remainder of the job.
During another project, the temperature dropped again at about 10 minutes into the job. At 190c I paused the job. Again, after cooling down and reheating, the nozzle slowly went back up to 210 for the remainder of the 2 hour job.
During these fluctuations, the heatbed stayed at 60c.
Does anyone have any suggestions on why this is happening, or what can be done to fix this? Could this be a g-code issue? I am using Prusa Slicer.
Thanks.