I didn't write crash, I wrote freeze
When I select the new font from the menu it just freezes and I have to restart via the hardware button. I noticed this with epubs. The issue happens when selecting that particular font on most documents (and when you restart koreader the document is shown with the previous font, so you could go on forever).
I can't really find a pattern, that's why I was asking. Certain fonts are affected (Charis SIL), most fonts are not (Times New Roman, Georgia, Bookman Old Style, Elegant Garamond, Amasis, Gill Sans, etc.)