It's one thing to have "a corrosion or drive-train issue" that affects a model or series of models built with that design. It's another to repeatedly have the same issue, repeatedly say it's fixed and then have it turn out to be not fixed. Toyota light truck frames, Nissan CVTs and arguably Honda A/C systems are the quintessential examples of this (though in Honda and Nissan's defense, they never claimed to have ever done anything about it).

I'm not gonna comment on the Mercedes because while they definitely have earned their reputation for being expensive in old age I'm not familiar enough with them to pass a value judgement.