Hi,
1. I have enabled cron jobs for now and will test with a few more uploads and users and let you know if the issue still persists.
2. When i disable the the plugin the issue goes away and as soon as i reactivated it the issue came back.
3. strangely i have tested it again this evening and it seems to be working, i will keep an eye on it and get back you if it comes back.
Regards
Chris