Haven't seen many late model MB cats fail in that way. The BMW V8 has that happen all the time.
My main reason for answering is that you might not know that your catalysts are probably still in emissions warrantee. (8year? 80,000 miles) (not sure about the time but just had one of my 540i cats done a few months ago under warrantee (97 540i 51k miles).
Bosch Master, ASE Master, L1
33 years MB technician