I'm having some problems figuring out a system that it's stable for some values of its physical properties but unstable for others.

Even a basic example would help a lot, a dimension 2 is totally fine.

I do not have problems figuring out what mathematically robust stability means, but I can't find any physical example.

actually what I'm looking for is more likely a system that has a finite robust stability margin. outside references are good too, thanks in advance.