I was having trouble with the Leadstone Jetpack as well, here is the solutions I came up with that worked (SMP, 2.1.9):
Make the jetpack and then deplete all the energy from it (so you see the empty damage bar). Then change the particles that are associated with it (the recipe below the main recipe in NEI). Then the quest is able to be completed.
What I suspect is going on: Something weird is happening with the way that it reads damage values (metadata or NBT, I don't know enough to know the difference). I noticed when I craft it initially (regardless of method, made it in AE terminal, TC crafting station, and vanilla bench) there was no damage value/bar (or power value) listed. Looking at the quest book, it has a fully depleted power (damage) bar, so I had to "craft" a jetpack like that. Hence fully depleting and then changing the particles. I could be COMPLETELY wrong, but it worked for me, hopefully it helps others.