ORIGINAL: Howler
did ya happen to notice if the glue was sticking on the shaft, the fletch that fell off, or both. If there is no glue sticking on the shaft where the fletchings fell off, then you'd know the glue didn't bond to the shaft, and visa-versa on the fletch. Sounds like the glue isn't bonding to one, possibly both, surfaces!
I agree, then you need to figure why.