I have been plagued with the Harman XXV "squeal" for about three years now. I have tried everything that I could find online, but nothing worked. I am proudly announcing that I think that I finally figured it out, once and for all, and it is not at all related to anything that I have found in any forum. Forget about cleaning your stove, buying better pellets, oiling here, graphite there, tighting bolts, lostening bolts, and all of the other nonsense. This was an unintended design flaw in the auger that turned the auger into a tuning fork. Don't believe me? Check out the video that I made.............. I plan on taking the auger to a welder to have some additional welds put on the shaft so that the vibration will go away. I would assume that this flaw is also the reason for the same noises in some other Harman stoves. I hope this helps other people. This has driven me crazy for the past few years, and I know that this will fix it.