Sure, but you don't need to know which butterflies flapped their wings - you just need to know "if there's a tornado, the house falls down, and we're in tornado

Sure, but you don't need to know which butterflies flapped their wings - you just need to know "if there's a tornado, the house falls down, and we're in tornado country." In the example above, it seems sufficient and entirely testable to conclude, if for whatever reason NFS is flaky, $PATH resolution will skip the directory with the right linker and fall back to the old one, and if for whatever reason you call the old linker, it has different behavior about static initializer order. That's enough to both describe the problem, reproduce it, and fix it. No, you're not going to be able to identify which particular packet was lost, but (and I say this as someone who's maintained production systems that rely on cross-continent NFS) you expect that packets can be lost and you figure out how to make the system robust against it. Don't put multiple files with the same name on $PATH, or call the linker by its full path, or something. And that leaves you a very far distance from "something spooky is happening with the computer and so passwords weren't being checked today, who knows."