W: Discarding reconstruction... -- WHY??

[tksharpless]

I've got several image sets that COLMAP aligns perfectly, giving sparse models that work fine when imported into other tools but which COLMAP itself fails to process into dense models. After what looks like a successful image registration stage, it issues one or more error messages about being unable to find a good initial pair and quits. I need mesh models and would like to generate them with COLMAP in the same script that creates the alignments.
This failure is very frustrating, and there seems to be no documentation on how to work around it.
Can you help?

[tksharpless]

The 'automatic reconstruction' tab of COLMAP GUI reconstructs these image sets OK when all images are in one directory. I have been using 'rig' mode, with the images in a directory per rig camera, so maybe there is a bug related to that.