DPF knocking

I have a knock occasionally when pulling away quickly or reversing on lock that sounds like it is coming from the front of the car somewhere. I have been back to the garage where I got the car from and they have told me that the DPF filter appears to be moving/twisting in it's bracket which is causing the knock. There is also soot particles all over the bulkhead round by the turbo and DPF so something is leaking. Has anyone heard of this or experience this before as I thought it could be engine mount or bush etc but they are all ok?

Car is a 2.0Tdi dsg on a 07

Thanks