Back when Heathkit (Or GriefKit as we called it for obvious reasons to be explained.) made kits they had the following problems that I am aware of:
Diodes marked opposite to their polarity: IE the Cathode band on the wrong end.
Resistors with the wrong color bands on them.
I had friends who encountered this, and it was a nightmare to track the problem down.
So if you get your hands on a GriefKit that "Never Worked" look for these things. It may save you mass headaches.
Of course, the bright little "Tom Edisons" that used liquid solder to put the kits together, acid core solder ("You mean there are different kinds of solder?") or the ones who cant follow a pictorial diagram; are amongst the real "Darwin Award" winners. I have seen these and more in my years of servicing.
(I don't disparage the one color blind chap who couldn't read the color code on the resistors either. He never knew he couldn't differentiate colors till he put a kit together for the first time. Then he found out he couldn't tell some colors apart. I helped him get that one going. it was pretty minimal to put the resistors in the correct locations.)
When I was starting out in electronics, one of my best friends held an advanced class ham lic, and a 2nd class radio-telephone lic w/ radar endorsement before he graduated high school. He never knew he was color blind untill he went into the Navy and they found he was color blind during the physicals.
I always make it a habit to check any part before installing it, even if it's a new part right out of the box.
I am glad I did that on the HeathKits I put together.