I wonder whether the paragraph style for the italic is inheriting the alignment from the Paragraph styles for the text.
Try using "Align Center" instead.
Thank you Derek and Ellis,
I'm not sure about whether the style is being inherited (where would i check that?) but Align Center did not help anything, sadly.
I ended up going into Sigil and changing the CSS, which indeed had been exported as "justify" and switching it with "center"... Since I have to go into Sigil anyway for images, I'll just have to accept that as being the only fix for now.
Sounds as if it was inherited, you can check this is your document's Paragraph styles.
Adobe's recommend workflow is to produce your ePub from InDesign, exporting it as an ePub, checking it, and if something's wrong going back to InDesign to correct the issue, before exporting and checking it again.
You might also check it in a validator, such as http://validator.idpf.org