I don't know if this is the same problem, but I had trouble training construction workers too. But in my case, I just stuck with them for a while (at least a few minutes) and they eventually caught on.

If they just stood there, I'd drag them at it again. If they tried and shook their head "no", I told them "Yes" with my stylus by dragging them at it again. Most of the time it took 3 tries, sometimes up to 5 tries, but they eventually got the hang of it.

Even then, I would watch them until thier status went from "untrained" to "trainee" at least, or else they would wonder off easily. This worked with any but the rare reeeeally stubborn ones who just didn't want to do construction.