I'm also a Manning author and this also happened to me a couple years ago. Amazon was allowing a counterfeit Kindle edition of Classic Computer Science Problems in Python to pose as legitimate on my own book's page! Only emailing Jeff got a solution. Manning seemed powerless to solve the problem themselves. I still have some bad reviews as a result of that counterfeit Kindle edition that plague my book page. Totally unfair!
Here's my original Tweet thread about it: https://twitter.com/davekopec/status/1302578592552022018
Here's the Hacker News discussion about it: https://news.ycombinator.com/item?id=24399301