The backup on my development server is failing with the error message "76% - Assembling the tsbak archive failed". Oddly, it was working for several weeks after the upgrade. This makes me think it is server related, but I unable to see what is wrong. The run-as account has full-control on "D:\Tableau\data\tabsvc\files\backups". Any ideas...?
Upgraded to 2018.2.3 to see if it would resolve the problem. The backup still fails in the same step, but it does run much longer before failing (maybe that's a clue). Anyway. I opened a case with support. I will report back when the problem is resolved.