In their world, it gives them the wrong answer that kills their dog, but it's fine because they never know because they don't look anywhere else. The dog dies, they're sad for a while, get a new dog, get on with their lives.

There's no reason not to trust it because since they trust it, they don't percieve anything wrong. They just take it and whatever happens happens, no annoying conflicting info and certainly none of that old grampa thinking and working and giving a shit about anything.