Dissolve in Avisynth repeating all the clips again

[Master Tape]

I'm having a bit of a problem trying to use the Dissolve function. I want do a crossfade between clips for a smoother transition, but after it gets to the last clip in the sequence it then crossfades back into the very start of the first clip and repeats the whole process again. Am i missing something?

SetFilterMTMode("DEFAULT_MT_MODE", 2)
SetFilterMTMode("QTGMC", 2)
a = AviSource("I:\Folder\Edit 1.avi").AssumeTFF().ConverttoYV12().QTGMC().Spline64Resize(1024,768).Crop(0,0,0,-6).ColorMatrix(mode="Rec.601->Rec.709").SMDegrain(tr=3,thSAD=1000).Prefetch(5)
b = AviSource("I:\Folder\Edit 2.avi").AssumeTFF().ConverttoYV12().QTGMC().Spline64Resize(1024,768).Crop(0,0,0,-6).ColorMatrix(mode="Rec.601->Rec.709").SMDegrain(tr=3,thSAD=1000).Prefetch(5)
c = AviSource("I:\Folder\Edit 3.avi").AssumeTFF().ConverttoYV12().QTGMC().Spline64Resize(1024,768).Crop(0,0,0,-6).ColorMatrix(mode="Rec.601->Rec.709").SMDegrain(tr=3,thSAD=1000).Prefetch(5)
d = AviSource("I:\Folder\Edit 4.avi").AssumeTFF().ConverttoYV12().QTGMC().Spline64Resize(1024,768).Crop(0,0,0,-6).ColorMatrix(mode="Rec.601->Rec.709").SMDegrain(tr=3,thSAD=1000).Prefetch(5)
e = AviSource("I:\Folder\Edit 5.avi").AssumeTFF().ConverttoYV12().QTGMC().Spline64Resize(1024,768).Crop(0,0,0,-6).ColorMatrix(mode="Rec.601->Rec.709").SMDegrain(tr=3,thSAD=1000).Prefetch(5)
Dissolve(a, b, c, d, e, 30)
Dissolve(last, a, 30)
Dissolve(last, b, 30)
Dissolve(last, c, 30)
Dissolve(last, d, 30)
Dissolve(last, e, 30)

[davexnet]

The first dissolve combined the clips with a 30 second overlap.
The succeeding dissolves re-adds the clips again, just as the comment mentions
in the example script on the dissolve avisynth webpage