Any inputs on the above issue?
Back in August, I had a similar issue upgrading our QA server from 10.1 to 2018.2.0. I'm sorry I don't remember anything more specific, but I believe the issue had to do with the backup repository location. It may have been some new configuration that was defaulted to a location where the BU was not, you might want to look down that trail especially if you're coming from 10.x. It's backup location was different. Hope it works out quickly for you.