I’m having the same problem. Reduced the size to 50 then 25mb. I did get one successful backup, but it took 3 days to complete. I haven’t gotten a successful backup since then. Here is a link to my log file:
https://www.dropbox.com/s/d9fvburv95qezs7/exptv-updraft-log-05082019.txt?dl=0
Any ideas?