Ah, I think that’s the problem. I’m opening Unreal and the USD stage from Windows, but I’m overwriting the files from a linux machine over the network. I’m assuming I’m actually not supposed to be editing a .usd file while it’s open within Unreal, and normally it would give me an error, but since it’s over the network, the permissions aren’t as strict.
I do get the same error as you when I try to write over the file from Windows.