UploadComplete not firing even though upload progress reached 100%

Uploading several small (20KB - 50KB) files. 1,2,… and even 6 files at a time (using WebFileUploader) works OK. Once I get to a point, typically about 8 files or more, I will get the 100% progress, but the UploadComplete event isn’t firing.

This is on a Xojo Cloud app deployment.

Any clues on why the UploadComplete event isn’t firing?