Catalytic Converter Question

[gromhome]

2nd owner - 2007 38J with 8.1 Chevy V8. Have Banks exhaust installed. Headers two exhaust pipe runs with cat conv on each pipe. One cat is now making a clanking sound like something is loose inside. Anyone here of this happening? Just made a ten day drive where it was flawless. Shut it down last night and start d it this morning and heard the clanking. It's loud. Thought it was transmission or engine at first but it's running well and when I crawled underneath it was clear where it was coming from. Anyone ever here of a catastrophic failure of a cat like this?