Alternator...fried...twice?

[CLS70]

Hi

A couple of weeks ago, got the Red Battery alarm "Charging System Malfunction"), shortly after car battery died, all sort of error messages but I knew it was electrical related.

Went through troubleshooting (checked Battery, Ground Straps replaced,...), managed to confirm alternator (180A Bosch) was out.

So installed NEW alternator, fire up right away, car worked fine, charged battery and displayed 13.5-14.2 V when running, all error messages went away; took it for a spin and then suddenly died again....same error.....no more charge....

So got a replacement unit (NEW), re-installed, replaced belt tensioner, belt and idler pulley. All worked fine for 5 days, no issues, then suddenly, "Charging System Malfunction" again, and voltage dropped to 11.5v (when running), measured at alternator, same value......

What are the odds of having failure of two new alternators.....what am I missing?

Have checked connections and fuses but can't find anything wrong but definitely there should be a reason for the failure.....any ideas?