Pocketbook Era not displaying the correct CSS styles

Hello everyone,

I have a problem with my Pocketbook Era, using an epub I made myself.
For reasons I don't understand, the Pocketbook doesn't follow the css :

• Only one of the two fonts I've embedded in the epub are displayed (and it is displayed on Sigil and Calibre) ;

• Pictures, that I set up to be centered and to take up to 85% of the page width, are all over the place.

What bugs me is that everything is displaying fine on various readers (Calibre, KOReader, etc.)...
Are you aware of CSS restrictions with Pocketbook ?

Thanks in advance !