Hi,
Thanks. It looks like the webserver doesn't provide enough resources to create larger zip files. To work around this, do this:
1) Go to the UD 'Settings' tab
2) Scroll to the bottom, and open the 'expert' section using the link there
3) Change the 'split' size down to 75Mb
4) Save settings
Then, start a fresh backup.
Best wishes,
David