Not enough info.. We could do with seeing underneath the car.
I imagine you haven't pushed it further down on the sleeve joints.
They are a right pain, I have had many different types of exhausts over the years and they have all banged and knocked bar one - a Yozza is the only one thats fitted first time and never knocked.
Best advise I can offer is try to get the exhaust slid into the sleeves as far as possible
Message btm in traders section mate they do them still