There were a lot of reports of numerous bugs in AC Unity. I too have noticed this, but to a much lesser extent than most. In the almost 3 weeks I'm 2 times fallen through the floor, and stayed 2 times hanging on a texture. Here I have stopped a long time in Paris, including the completed campaign, countless side missions and some multiplayer sessions.
That was it even with the bugs that I have experienced. It is now time really nothing as bad as it looks.
The game itself is a worthy part of the series and the first AC that I really had a lot of fun.