I tried to update to 4.0-beta.4 from within JEB, but just "downloading..." was kept shown and no progress.
I gave up and tried to download the update via a web browser, and found the downloading session terminated, resuming several times and finally finished.
It may take a long time when downloading within JEB too.
I think it may be a good feature for JEB to show download progress information (or, alerts when the download session fails).