There's tonnes of bugs remaining to be fixed in the notoriously buggy Assassin's Creed: Unity. Over 300 bugs in fact, according to notes for the game's forthcoming patch. It'll be the third patch since the game launched two weeks ago, but it won't be the one to specifically address the game's framerate problems, with Ubisoft writing that this will be the theme of a future patch.
As for this particular patch, the notes are extensive so you'll want to read them all over here, but some highlights include fewer instances of Arno falling through the bottom of the map, fixes to cooperative matchmaking and a whole host of fixes to specific missions.
The full notes are of Tolstoyan proportion so set aside an afternoon. It's due to release for PC later this week, and follows a pretty hairy November for Ubisoft, with ongoing issues affecting both Assassin's Creed: Unity and Far Cry 4. Tsk tsk.