I am having the exact same issue. It's incredibly frustrating. I've used unBalance on this array in the past (several months ago) without issue.
I am attempting to move data from one 8TB drive to two new 6TB drives so I can remove the 8TB from the array.
I've disabled both VMs and Dockers from the settings menu.
I've also disabled the cache drive for the folder I am attempting to work with and set Mover to a monthly schedule.
I am able to select the source and target for the scatter and select the 'plan' option, but cannot select the copy or move options.
(EDIT) It finally worked with these changes - I just had to run through the planning stage first. The banner at the top never went away, but it's finally scattering the files.