5.79.3 / 5.81.0
All of my backups work (now), and speeds range between 5 MB/s to 20 MB/s.
Most of my VM's are smaller (zstd helps a lot), though the largest archive is about 80 GB.
Also, all of my backups are sequential -- I seem to remember a previous note where somebody had problems with concurrent uploads.
My XOCE VM runs with 12 GB, which was the number that "just works" according to some of my earlier problems (and I haven't bothered to chase down or fine tune further).