Other contributing factors: The thread is shit, and there weren't enough stitches per inch. Also, the fabric doesn't have the tightest weave, which helped it fray at the end and pull out of the stitches after the main seam failed.
Took everything mostly apart on the blown strap and resewed it, and reinforced the other strap. This pack is a fully padded camera bag so it was nice to have the post-bed machine. I had started sewing it on a flat-bed, but it got too hard to keep the bag in place.