Unfortunately things are not sounding that solid even on new code, and even rclone breaks sometimes.
Still, there seems to be a bit of improvement. Does that sound like an accurate summary of posts here?
Yes, that seems accurate. Backups that have a small amount of data to upload seem to be fine. Backups that have a large amount of data seem to still fail. When they do fail, they seem to fail at whatever the last steps of the backup are (usually around the part where it says: Deleting unwanted files …). Let me know if you guys need more specific logs to help with the cause.