Hi Rob,
Sorry to here about the re-test thing, but it is cool they will let you take it again. Did you bust both the 3G & 2G (using backing strips) welding with 7018 all the way??? Remind what positions those are because I have forgotten. 2G = plate/joint horizontal? 3G= plate/joint vertical? Anyway, regardless of the position, you probably had lack of fusion which means when the bent the specimins.....they cracked on the root side. Really could have been the face side too, but you'll need to find out those details. Really hard to say what happened, but I know this.......IF you cracked a root bend, it is probably because you had slag inclusions or you long arc the root pass. Generally speaking, it is hard to crack 7018 unless you had too much heat or moved too slow or long arced the whole thing. Again, need more information. Try to run a bit cooler on the vertical pass, say 90-100 amps and paying extreme detail to your arc length. Give us some more details and then we can do the same.
Be well,
Hawk