Yeah, January 3.5.1 was the last update.
It might be weirdness in the EPUB that yours is handling differently?
There's always the "nuclear option". I have a little Windows executable that just strips all the CSS out of an EPUB. It can work with DRM'ed files without un-DRM'ing them. It's named "unduke.exe" after the horrible formatting of "Duke Classics" (with the dog in the corner of the cover). This will leave your EPUB default formatted. It's on my website under Android > Win32 Tools for Android. It's not reversible unless you saved a copy.
Code:
C:\>unduke.exe italicbook.epub
It could also be that they never closed an <i> and whether this affects display is determined by where you have read.