Hi Thorsten,
I've already fixed the dashboard! 🙂
It now flags based on the schedule (before, anything over 7 days triggered action needed).
Schedule for the "action needed" flag now:
daily > 2 days overdue
weekly > 9 days overdue
monthly > 34 days overdue
off never by age.
Please try the (manual) backup on the problem site again with version 2.6.14.
The failure might be fixed with this, and the dashboard will specify any errors. There's no size limit.
Cheers
Pascal