Yes, they are human - even though - we pay them to make sure things are in order - they can foul up, too.
I have a special little too that I use to tighten my needle screw - sure works easier than the screwdriver for me. It also can be used to help tighten my hoop adjustments. Don't know what I would do without it. And you are so right - just because someone has worked on something does not mean that it is correct. I had my oil changed in my car, and when I went back to work I saw oil under my car - the mechanic forgot to put the plug back in - so back to the shop.