[gontofe]

So I had this earlier, it downloaded the part update and nothing more. However, I switched to ak-team and everything worked.

You should see the zsync file in the ota directory (downloaded from ota server) and the installed tar (built locally) when ota starts. Then Koreader uses zsync and package index to determine delta to download (and builds updated.tar). Once download has completed successfully you should see a message saying Koreader will be updated after restart (and you will indeed see the new version after restart).