When I turn a blank, I get it down to a reasonable width with tools, then I go the rest of the way to the bushings with sandpaper. I've never had an issue, however, I was working with some spalted oak in a slimline style and I noticed that one side of the blanks was flat and even with the bushings while the other sides were still thick. I kept trying to sand them even and round but it just got worse. Eventually the flat side was even becoming indented while the other sides were still thick. I thought maybe my mandrel was bent but I fixed the problem slightly by getting my tools out and lightly running them down the blanks. It evened them out. Any ideas? Was the grain on that side of the blanks softer maybe and more likely to quickly sand down compared to the other sides?