Actually I’m not able to reproduce this, but because I’ve seen this 2-3 times in the past, I know what you’re talking about. Having said that I don’t know how exactly this happens, but restarting KopiaUI fixed the issue for me.
Basically for some reason when this happens, kopia reads the directory but it finds no files in it without any errors so it creates an empty snapshot. I suspect some kind of permissions issue.
This should be easy to remove using kopia snapshot delete from CLI, unfortunately the UI option is not available (yet).
If somebody finds a repro sequence that reliably triggers this, definitely let us know here.