I played through it a couple of times. I think I get your problem. The
slide parts are done with vibrato so your sliding back and forth over the fret in question. I remember from your last post that you like a light slide so you will need to have very sensitive hands to apply the right amount of preasure.Again, lots of practice.
EDIT I am talking about the slide tune, I just realized you are talking about the other two lessons so for those it is just practice for accuracy.