World Import fails

I am using the Import Wizard to upload my local game world.
Importing assets works but creating the world fails because:

And now I don’t know. What is the actual error?

It sounds like the connection gets interrupted, have you tried again? Do you have a stable internet? How big is the world?

Hm, I don’t know what happened here. I deleted all files on The Forge (again), closed my browser, and retried. Now it works.
The connection was stable from the start. The world file is 80MB zipped. Maybe some artifacts in the browser cache?! Anyway, it works now.

Highly recommend in future that you DO NOT delete all your files on The Forge, as doing a re-import will skip anything already imported (sometimes avoiding issues where there was instability in the connection, simply by not having to do as much work)