TOPIC:

We see a strange phenomenon that when my co-author creates new learning objects in a subfolder, they do appear twice for me as the creator, once in the subfolder and once in the root. When I drag them from the root to the subfolder, they will disappear from the root and remain only in the subfolder. This happens with a clean browser, so it's not a browser caching issue. It seems to be a bug.

Yes, seems like a bug. I'll try to replicate and create an issue on github.