Subsetting fonts may have removed Italic (if it was improperly declared and used) glyphs.
A font family can have 4 members (files):normal, bold, italic, bold italic
I have seen mismatched @font declarations (does not match the font file attributes)
Don't embed any fonts and see if the device renders italic (in the proper places
)
If that works
You need a fresh (full sets) version of that font family member to embed. DO NOT subset