Please update to the latest version 7.8.1.351.

Thanks Alex, that seems to have solved that issue, the backup is getting a lot further than before but stops reading files after a while with the "waiting for 60 secs, will keep retrying for 1:09:37..." message. This is weird as it continues to upload to cloud, with uploaded size being greater than read size... any advice?

If it's still running, give it some time. I assume you're running an image-based backup. Depending on the size of your data set initial upload might take quite some time