[pierotofy]

I can chime in on the road: there's probably insufficient color variation and that gets filtered out during patch-match. You can relax the NCC Threshold parameter and you should be able to reconstruct the road (you'll also get more outliers in other areas though). There might be an option in COLMAP to do that. In ODM you need to modify the fNCCThresholdKeep parameter in OpenMVS (you'll need to recompile OpenMVS).

[Enginerrrd]

That's an interesting idea. I'm a bit skeptical though, since these were dirt and gravel forest roads with lots of different colors and apparent features.