Backup to cloud never finishes

Hi
I’m running Comodod backup 4.2.2. Backups to a NAS drive run fine. Backups to the cloud seem to be running fine until right at the end when they always fail to back up the last 4MB of data. It doesn’t stop, no errors, but just never finishes. This is trying to backup around 1GB of data. Does anyone have any ideas please?
Thanks