I would recommend excluding or deleting some very large files I see in your site's root that seem to have nothing to do with your site's operation (they do look like temporary files):
zi0ElmCB
ziEeqqNU
zieSnjIm
They seem to make up more than 90% of your backup's size, they are VERY slow to backup (since they are 270, 780 and 440 Mb respectively) and they are not needed. I would guess that this is why you get frequent backup failures.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!