If this is a book that has a stylesheet altered by Calibre, go into "Look and Feel" in the conversion tab. Go down to Filter Style Information and check fonts (and margins if they are not adjusting). I have 32 drm free ePUBs on my Go at the moment and the fonts change on all of them. I did not have to make any changes on books that simply lost their DRM, but I did have to make the changes in Look and Feel on books that someone else had converted or altered in Calibre before I got them.
I really want to thank you for this information. I have been using calibre for years and I love it but I never knew how to resolve this issue. I side-load a lot of books and this was most definitely a game changer for me!
I now have only one formatting issue that I have not been able to resolve and that is inconsistent bottom margins when viewing side-loaded books.
Is this a common problem for others as well & is there a solution?