I have been using Klipper for a few years now with out issue. Today, in the middle of a print, I noticed that the machine shut down (Lulzbot TAZ6 with dual v3 Extruder running an Archim2 controller board). I run Octoprint with the Octoklipper plugin. Again, never had any issues in the years using this config. The machine stopped due to an error that was detected where the hotend temperature was not responding as expected. The temperature plot Octoprint showed that the temp started dipping and jumping erratically. So, my thought was that the thermistor was failing or had a bad connection. I replaced it with an identical sensor and got the same error again when I heated it to test. I swapped sensors with the other hotend and got the same issue again. I attached K thermocouples to the heater blocks and confirmed that they are heating at the same rate and the heater on extruder 2 reaches and detects the proper temperature, but the temp sensor for channel 1 always started lagging behind at ~125C. The result is that the temp increase detected slows down so much that the printer shuts down, or it actually gets to the target temp reading, however, the actual reading is ~40C - 50C higher. Again swapping the temp sensors yields proper readings on channel 2 and incorrect readings on channel 1. This rules out the sensor or the heat cartridges being a problem. It just seems to not be reading the channel properly all of a sudden.
I read that there are ways to manually tune the temp profile of a sensor vs using the standard sensor selection, but that seems like a bandaid. Has anyone experienced this behavior or have any ideas of what to look at next? My thought was to tear down the machine and start probing the Archim board temp circuit to the ADC, but its a lot of invasive work that I would like to avoid if possible.
Below shows an example ramp up of both extruders with channel 1 (red) starting to deviate ~125C. When Channel 1 reaches the 210C target (assuming it does before the printer shuts off) the measured temp of the block is ~255C - 260C
Thanks!