The Motor could be tested for squeaks, by removing the Belt and try turning the Motor Shaft by hand.
Does it turn easily, smoothly ?
Can you give the Motor Shaft a twirl and will it continue to turn a little by itself ?
I installed the maintenance kit today and so far that seems to have done it. The motor does seem to turn pretty smoothly. I can spin it by hand and it will continue to spin a bit by itself.
Word of warning to anyone else installing this maintenance kit: the worst part, by a long, long way, was dealing with the plastic tri-rings at the base of the shaft. There has to be a better way, because there is no way the pros would spend about 10 minutes per shaft working with those things. I can see a need for the perfect tool - some sort of three-pincer pliers that equally compress the three corners of the triangle to expand that ring out enough to slide down to the base of the shaft. Because, of course, it's easy to get it onto the first indent, but getting it past that was just freakin awful. I finally just manhandled it enough to get it down there. After four times I did not find any good technique. Hopefully I did not shorten the life of the material. It was also tough getting the old ones off the base of the shaft. But I finally decided that I didn't care since I had replacements, so I either broke them or stretched them way out to remove them.
Everything else went very smoothly and the videos and the help here were really key. I suspect the issue was either or both of the belt tension pulley or one of the drum rollers in the back. Thanks everyone for the help.