Hi all. It does look like outer pipe is not sliding correctly. If it's welded on both end's or not I can't comment about but they need to move. Here is an example of good pipe. It finally gave away after 60 engine hours and 6 years of use. It still was not due weak pipe but loose mounting strap and engine misalignment instead. It did have plenty of broken welds and some hair cracks already.

Anyway this beeing well used one can see outer shell grinded grooves about 3mm in lenght. While taking picture it was 11C. In fight it is hundreds of degrees and it's visibly longer. This happened to have aluminium outer pipe but it makes little or no difference because of huge temp difference.

Check you pipes annually

/Jyri