I found out after making this topic that you need to run a command on the console when you expand your digital ocean volume. So effectively I was not using all of my 300gb.
I fixed that and changed nothing else and I had the problem reoccur today. There were 2 unzipped tar files and 3 gzipped ones when my site went down.
I will try the strategy discussed above next.
But what I wanted to say is that it would be nice to have an indicator on the admin UI that there are failed backups. Or maybe clear out any *.tar when triggering a new backup process? In this case, I had 90GB of unzipped backups that can’t be seen from the admin UI. And also no “backup failed” DM from either