Outline Editor - sometimes won't save my changes

Hello again - recently upgraded to 21c marketplace from the 11's on prem. Each month we have a few outline changes to make relating to moving members from one group to another, adding new members. Typically i would just do it in the gui interface. Find store X, cut it from where it was, and move it to where it needed to go. Repeat till done. re-load new data. Calc database - Presto! all done.

This is my first month trying that in 21 c. I keep getting "Failed to Save Outline. Cannot build dimensions. There are other active users on Database." BUT there aren't - my users don't even have accounts yet.. its just me!