File upload issues

It seems that occasionally file uploads can go missing. I think I need to look at the file upload queue and see if there are any noticable issues when uploading multiple files at the same time. I think what might be happening is, when multiple files are uploaded the file upload process as a whole is completed before the rest of the uploads are finished and may actually cancel.

I may possibly be able to simulate this by adding a delay multiplier to file uploads so that the first upload has no delay, second has say 1 second, third has 2, and so on.