Any time a car reaches the point of rusting where a major structural failure occurs (I would classify suspension components falling off as major) it is a definite cause for concern and time for a thorough inspection of the whole body to find any more rust that might be hiding under body seam joints or undercoating as they won't always make themselves visible without good checking.
My 80 has a known rust issue before I ever got it back on the road, wasn't bad enough to retire yet but wasnt really worth sinking much into either as it's time was definitely limited with hefty underbody rust. I just reinspected it yesterday, it appears the undercoat has some fresh looking rips in it where a gap has appeared between the floorboard and the front subframe runners that go under the footwells, knowing my rocker has bad rust in the same area, it will need a hefty looking and may result in finally retiring the car if it really is separating as it looks to be. Just means I have to step up the restoration of the 82 a little,lol.

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Chris
64 190D R.I.P.
80 240D W/617 engine -for sale
82 240D -for sale