Amazon occasionally has difficulty displaying italics in certain fonts in their digital previewer. This typically only affects Libre Baskerville font.
Our programmers are working on a way to address these issues but in the meantime, we have found a relatively simple solution that seems to be working well:
Open your Atticus exported PDF in Adobe Acrobat Reader
Choose File and then Print
Under Printer options, choose Microsoft Print to PDF
Under Page Size and Handling, make sure it's set to Actual Size
Also ensure Choose paper source by PDF page size is checked
Click Print and it will ask you to choose your location to save the file
Save it with a slightly different title, just to be sure it uploads as a completely new file into KDP, and it should work!