In other words, they failed to do end-to-end testing in some cases. They tested pieces, but not the full system they released. If you don't test each config up

In other words, they failed to do end-to-end testing in some cases. They tested pieces, but not the full system they released. If you don't test each config update, by definition you didn't test it. Rust has many nice properties, but it can panic too. You should still test the whole system before each release if it's critical.