UpdateBuilder - Failure during upload

I needed to release an update to our internal application s few minutes ago and on starting UpdateBuilder, it said there was an update. I updated and proceeded with the release as usual.

This is a simple update with two files, an executable that is CAB compressed, and a report template, which are uploaded to a regular public file share on a Windows server. The update process proceeded as usual and compressed the exe to a CAB, but at the point of transferring the files, which usually takes about five seconds, the progress bar ran instantly to 100%, the status box said "Update uploaded" but an error dialog popped up with "Failure during upload". No files were uploaded.

I rolled back to an earlier UpdateBuilder that I had on a VM (V2.1.2.0) and the update ran to completion. I updated to the latest version again (V2.1.3.0) and got the same error message and failed upload.

What upload type is this?
We are not aware of issues. If you have more details (when needed send it in private), we can investigate it.

Just a plain old update to a shared network drive. The drive has read/write access, and it works fine with the previous version of UpdateBuilder.

Not sure what other information I can provide – if you can think of anything specific, I can send it.