I had gotten some less than stellar cuts on a small item I was working on. I hadn't checked the alignment on my saw in a while. Lo and behold, I was out when the blade was tilted to 45*. The 90* was off a bit more than I had achieved last alignment so; seasonal change? Temperature? The fact that I am checking with an alignment plate instead of a blade? At any rate about 30 minutes of effort has it back to within a thou and the problem cuts are now as expected.
I had always had a bit more runout than I liked but, not enough to get too excited about. Some other generous person had posted about using stones to true up the arbor plate. I used a small stone that I normally use to round bandsaw blade backs. I followed that with a medium, fine and extra fine diamond stick and all but eliminated the runout. After that alignment was even easier than usual. Just a nod to occasional checkups even when you "know" things are OK.