Addendum to 2: never believe that what they say is relevant to what's actually happening here. You have a lot of faith that the people writing error messages knew what they were doing!
Having written some error messages in a godforsaken database frontend, an error message only means that something didn't work correctly and may or may not correctly indicate what is actually wrong
I don’t know, have you ever used JavaScript? I’ve run into some really fucking weird bugs. I’ve also spent hours trying to find the source of an error message only to discover the error message was lying and caused by some other error.