A different print fan failure from the one currently being discussed
After a few hours of printing flex 98A material very slowly, my kit-built MK3 failed with a print fan error. It looked like the symptom that was called out in the 3.1.2 firmware release notes, that printing a long linear line very slowly could cause a stray fan error, but that was fixed then, and I'm on 3.1.3.
The good news is: I told the printer to resume printing, and it picked up right where it left off and my 15 hour print was overall a success and totally usable.
Self-test passes.
Any other suggestions for debugging? Just hope it doesn't return?
One more thing I feel compelled to say: I couldn't be happier with my purchase. Build was awesome, instructions were perfect and the results are great. I've made my son's toys way better, fixed things around the house and garden, made things for friends. My 3-year-old loves to watch as it prints. I have had a few issues, but each time the printer, support or community has come through with a reasonable solution in a very short time. I wouldn't hesitate to recommend this printer to anyone who was looking for one, and I'd happily help assemble another kit in exchange for beer and good maker company.
Great job Mk3, Prusa and Co, and everyone here!