Recently I was dealing with an unexpected issue raised by our Support customer, in which data became inconsistent after a schema change was applied. After some investigation, it turned out that affected tables had a special word in the comments of some columns, which triggered an already known (and fixed) issue with the TableParser.pm library [&]

https://www.percona.com/blog/2020/10/08/dangerous-edge-case-warning-for-percona-toolkit-and-pt-online-schema-change/