As I've been going back and retrying some of my content from Photosynth 1 synths, I've experienced more of this where I've selected a subset of 200 from a larger walk, etc. and uploaded a full 200 photo new synth only for it to fracture in the middle or at two points (making half to two thirds of the upload useless and therefore requiring a full re-upload of that range of photos to test those ranges as their own synth).
It's been making me wish that all photos that I've uploaded to at least Photosynth 2 could be browsed as a photo library for starting new Photosynth 2 synths.
Ideally, in future, I could select subsets of Photosynth 1 photos using a combination of:
1) an overhead view of the camera frusta (as seen in Henri's WebGL photosynth 1 viewer or Greg's iSynth app) which makes selecting spins, walks, walls, and pans trivial and
2) a chronological listing of images (useful for selecting ranges through an area with many overlapping camera positions).