Flushed with the success of my replacing the water pump and timing belt, I now move on to the exhaust...

A6 1999 V6 Avant Quattro 2.8 petrol

The exhausts both blow at the joint in front of the flexi bits. The local garage has redone the clamps numerous times and gunked it to high heaven, but it keeps working loose.

Is there an easy fix for this? The exhaust itself seems in fine condition - it looks like its made of stainless.

Thanks in advance.