#5. This one is interesting. The glitch you see here is caused by a very common shooting behavior that we generally can correct for, but couldn't in this case.
To see this behavior, hit the "m" key and look at the top of the arc. Note how there is a dense "outer" set of photos, and a sparser (but quite sufficient) inner set in that little region. This is case of what we call "overcompleting" the circle, and it is so common that we have logic to detect it, and ignore frames that seem to be part of such a "tail".
That logic only works when the sorting of the "DateTaken" field in the EXIF agrees with an angular sweep sort from the center of the reconstruction, which it will if people take the photos in normal spin order. Here's what Mike says about this one:
It wasn’t triggered because the time ordering was deemed unusable. There are multiple images with timestamp 1387624011 (i.e., 2013:12:21 11:06:51), and the timestamps are not monotonically increasing.