This was a couple weeks ago, and I’ve worked on 2 other projects since then, so I’m a little fuzzy about this… but I think I may have been mistaken about my quote above.
I think what was happening was that I would make a configuration change in my scene, which would run a MSH2RAD component, and according to what @sarith found, we have to do a manual post-process search+replace in the mesh and material .rad files when that component ran. We weren’t sure if that (.rad file corruption) was happening because of my scene or a bug in MSH2RAD, but I believe it was the later. I actually wanted to attempt to fix that bug (if it is one) when I got time as my first contribution to Ladybug Tools.
Anyway, if I didn’t do the post-process search+replace when doing my rendering, then that would trip Radiance with that error I believe. And that corresponds to what you found in the log.