@kript96: You'll have to reinstall basically everything except the JB after a FW update.
@ktos35l:
https://github.com/koreader/koreader...hich-do-i-pick &&
http://build.koreader.rocks/download/README (Spoiler: Pick PW2).
Launch KOReader through KUAL, don't try to open PDFs in the Kindle's UI.