Could this be related to the Dropdown menus spawn on other monitor issue?
Maybe not because that problem is kind of the reverse: open the popup on the primary monitor if the Slicer window is on a secondary one. But still it’s quite similar and the number of new screens seem to suggest there may be a connection.
@PaoloZaffino does this happen more if you open dropdown menus such as the module history button? Do these desktops appear all at once, or gradually as you use Slicer?