I remember once having to make a SOAP call that just wasn't connecting for some reason, but another end point on the same service was working, which made no sense. We tried calling the working endpoint right before calling the busted endpoint just for kicks, and that actually functioned. Still to this day makes no sense at all to me, we ended up moving off of soap eventually, but that code was in there until we did.
I hate the days when you are trying to fix a bug in a block of code and as you write pinning tests you realize that the code has always been broken and you cannot understand why it ever got the right answer. You’ve let the magic smoke out and you cannot put it back without fixing the problem. At some point you have to stop trying because you understand perfectly well how it should work and you need to move on to other things.