Have you personally faced these issues?
I've never faced knocking of any sort. Maybe fuel quality is a factor to be considered here.
All DCTs are jerky at low speeds, they can never be as smooth as a conventional torque-converter auto or CVT. Even BMW have these problems, so this is not something that is a fault of Changan.
Brakepad issues? If you're talking about the crappy braking, then I suggest to change the tyres. The stock tyres are absolutely pathetic when it comes to grip. They will wheelspin on the slightest amount of throttle when starting off, something that shouldn't happen in a 100 hp car lol.